| Transactions |
| Date | Team | Player | Type | OthTm | EffDate | When |
| 4/5/2012 | BRK | Cuddyer | Placed on Injured List | | 4/5/2012 | Before |
| 4/5/2012 | BRK | Punto,N | Promoted to active roster | | | Before |
| 4/7/2012 | ANN | Cingrani | Demoted to reserve roster | | | Before |
| 4/7/2012 | ANN | Mujica | Promoted to active roster | | | Before |
| 4/7/2012 | RMO | Rivera,M | Promoted to active roster | | | Before |
| 4/7/2012 | RMO | Dempster | Traded away | BBG | | After |
| 4/7/2012 | RMO | Peacock (AG) | Acquired via trade | BBG | | After |
| 4/7/2012 | RMO | Rivera,M | Acquired via trade | BBG | | After |
| 4/10/2012 | BRK | Buck,J | Promoted to active roster | | | Before |
| 4/10/2012 | BRK | Leon | Placed on Injured List | | 4/9/2012 | Before |
| 4/12/2012 | CIO | Bailey,A | Promoted to active roster | | | Before |
| 4/12/2012 | CIO | Jimenez,U | Demoted to reserve roster | | | Before |
| 4/12/2012 | CIO | Ohlendorf | Promoted to active roster | | | Before |
| 4/12/2012 | CIO | Sanchez,J | Demoted to reserve roster | | | Before |
| 4/12/2012 | CSS | Hanrahan | Promoted to active roster | | | Before |
| 4/12/2012 | CSS | Smith,J | Placed on Injured List | | 4/12/2012 | Before |
| 4/13/2012 | HHR | Pollock | Promoted to active roster | | | Before |
| 4/13/2012 | HHR | Walker | Placed on Injured List | | 4/12/2012 | Before |
| 4/13/2012 | NYD | Berken,J | Promoted to active roster | | | Before |
| 4/13/2012 | NYD | Dyson,S | Demoted to reserve roster | | | Before |
| 4/14/2012 | FDH | Cervelli | Demoted to reserve roster | | | Before |
| 4/14/2012 | FDH | Ramos,W | Promoted to active roster | | | Before |
| 4/14/2012 | RMO | Gardner | Demoted to reserve roster | | | Before |
| 4/14/2012 | RMO | Gose | Promoted to active roster | | | Before |
| 4/15/2012 | CIO | Escobar,E | Promoted to active roster | | | Before |
| 4/15/2012 | CIO | Young,Mi | Demoted to reserve roster | | | Before |
| 4/16/2012 | FDH | Boxberger | Promoted to active roster | | | Before |
| 4/16/2012 | FDH | Petit | Demoted to reserve roster | | | Before |
| 4/17/2012 | CIO | Grimm | Demoted to reserve roster | | | Before |
| 4/17/2012 | CIO | Wang | Promoted to active roster | | | Before |
| 4/17/2012 | FDH | Cashner | Promoted to active roster | | | Before |
| 4/17/2012 | FDH | Strasburg | Placed on Injured List | | 4/17/2012 | Before |
| 4/20/2012 | HHR | Beavan | Promoted to active roster | | | Before |
| 4/20/2012 | HHR | McAllister | Demoted to reserve roster | | | Before |
| 4/22/2012 | BRK | Bay | Placed on Injured List | | 4/22/2012 | Before |
| 4/22/2012 | BRK | Morgan | Promoted to active roster | | | Before |
| 4/22/2012 | FDH | Burton | Demoted to reserve roster | | | Before |
| 4/22/2012 | FDH | Fontenot | Demoted to reserve roster | | | Before |
| 4/22/2012 | FDH | Romo | Promoted to active roster | | | Before |
| 4/22/2012 | FDH | Stammen | Promoted to active roster | | | Before |
| 4/22/2012 | NYD | Familia | Demoted to reserve roster | | | Before |
| 4/22/2012 | NYD | Galarraga | Promoted to active roster | | | Before |
| 4/22/2012 | RMO | Herrmann,C | Promoted to active roster | | | Before |
| 4/22/2012 | RMO | Martin,R | Placed on Injured List | | 4/22/2012 | Before |
| 4/24/2012 | CIO | Stewart,Z | Promoted to active roster | | | Before |
| 4/24/2012 | CIO | Wang | Demoted to reserve roster | | | Before |
| 4/24/2012 | RMO | Odorizzi | Promoted to active roster | | | Before |
| 4/24/2012 | RMO | Rivera,M | Demoted to reserve roster | | | Before |
| 4/26/2012 | CIO | Germano,J | Promoted to active roster | | | Before |
| 4/26/2012 | CIO | Ohlendorf | Demoted to reserve roster | | | Before |
| 4/26/2012 | SOI | Axford | Promoted to active roster | | | Before |
| 4/26/2012 | SOI | Cook,A | Promoted to active roster | | | Before |
| 4/26/2012 | SOI | Hellickson | Placed on Injured List | | 4/26/2012 | Before |
| 4/26/2012 | SOI | Lidge | Demoted to reserve roster | | | Before |
| 4/28/2012 | CIO | Bailey,A | Demoted to reserve roster | | | Before |
| 4/28/2012 | CIO | Sanchez,J | Promoted to active roster | | | Before |
| 4/28/2012 | CSS | Dirks | Promoted to active roster | | | Before |
| 4/28/2012 | CSS | Ortiz | Placed on Injured List | | 4/28/2012 | Before |
| 4/28/2012 | NYD | Blackmon | Demoted to reserve roster | | | Before |
| 4/28/2012 | NYD | Thames | Promoted to active roster | | | Before |
| 4/29/2012 | HAR | Baker,Je | Promoted to active roster | | | Before |
| 4/29/2012 | HAR | Kipnis | Placed on Injured List | | 4/29/2012 | Before |
| 4/30/2012 | HAR | Chacin | Promoted to active roster | | | Before |
| 4/30/2012 | HAR | Melancon | Demoted to reserve roster | | | Before |
| 5/1/2012 | CIO | Mather | Promoted to active roster | | | Before |
| 5/1/2012 | CIO | Valencia,D | Demoted to reserve roster | | | Before |
| 5/1/2012 | CSS | Blevins | Demoted to reserve roster | | | Before |
| 5/1/2012 | CSS | Smith,J | Activated from Injured List | | | Before |
| 5/2/2012 | BRK | Feliz | Demoted to reserve roster | | | Before |
| 5/2/2012 | BRK | Humber | Promoted to active roster | | | Before |
| 5/3/2012 | HAR | Eaton | Demoted to reserve roster | | | Before |
| 5/3/2012 | HAR | Nava | Placed on Injured List | | 5/3/2012 | Before |
| 5/3/2012 | HAR | Parra,G | Promoted to active roster | | | Before |
| 5/3/2012 | HAR | Pearce | Promoted to active roster | | | Before |
| 5/3/2012 | NYD | Blanks | Demoted to reserve roster | | | Before |
| 5/3/2012 | NYD | Snider | Promoted to active roster | | | Before |
| 5/3/2012 | RMO | Odorizzi | Placed on Injured List | | 5/3/2012 | Before |
| 5/3/2012 | RMO | Pomeranz,D | Promoted to active roster | | | Before |
| 5/4/2012 | CIO | Romero,R | Promoted to active roster | | | Before |
| 5/4/2012 | CIO | Stewart,Z | Demoted to reserve roster | | | Before |
| 5/4/2012 | FDH | Cashner | Demoted to reserve roster | | | Before |
| 5/4/2012 | FDH | Strasburg | Activated from Injured List | | | Before |
| 5/5/2012 | HHR | Pollock | Demoted to reserve roster | | | Before |
| 5/5/2012 | HHR | Walker | Activated from Injured List | | | Before |
| 5/6/2012 | CIO | Hudson,D | Demoted to reserve roster | | | Before |
| 5/6/2012 | CIO | Noesi | Promoted to active roster | | | Before |
| 5/6/2012 | CSS | Flowers | Promoted to active roster | | | Before |
| 5/6/2012 | CSS | Ruiz | Placed on Injured List | | 5/6/2012 | Before |
| 5/7/2012 | BRK | Bay | Activated from Injured List | | | Before |
| 5/7/2012 | BRK | Kelly,D | Demoted to reserve roster | | | Before |
| 5/7/2012 | HAR | Melancon | Promoted to active roster | | | Before |
| 5/7/2012 | HAR | Parra,G | Demoted to reserve roster | | | Before |
| 5/7/2012 | HAR | Samardzija | Demoted to reserve roster | | | Before |
| 5/7/2012 | HAR | Vincent | Promoted to active roster | | | Before |
| 5/7/2012 | HHR | Rosenthal | Demoted to reserve roster | | | Before |
| 5/7/2012 | HHR | Veras | Promoted to active roster | | | Before |
| 5/9/2012 | RMO | Herrmann,C | Demoted to reserve roster | | | Before |
| 5/9/2012 | RMO | Martin,R | Activated from Injured List | | | Before |
| 5/10/2012 | CIO | Acosta | Promoted to active roster | | | Before |
| 5/10/2012 | CIO | Germano,J | Demoted to reserve roster | | | Before |
| 5/10/2012 | HAR | Laird,G | Promoted to active roster | | | Before |
| 5/10/2012 | HAR | Navarro,D | Demoted to reserve roster | | | Before |
| 5/11/2012 | CSS | Gonzalez,Mic | Promoted to active roster | | | Before |
| 5/11/2012 | CSS | Stults,E | Demoted to reserve roster | | | Before |
| 5/11/2012 | SOI | Hellickson | Activated from Injured List | | | Before |
| 5/11/2012 | SOI | Penny | Demoted to reserve roster | | | Before |
| 5/12/2012 | CIO | Lavarnway | Demoted to reserve roster | | | Before |
| 5/12/2012 | CIO | Nickeas | Promoted to active roster | | | Before |
| 5/12/2012 | CIO | Sogard | Demoted to reserve roster | | | Before |
| 5/12/2012 | CIO | Young,Mi | Promoted to active roster | | | Before |
| 5/14/2012 | CIO | Matsuzaka | Placed on Injured List | | 5/13/2012 | Before |
| 5/14/2012 | CIO | Volstad | Promoted to active roster | | | Before |
| 5/15/2012 | BRK | Parker,B | Promoted to active roster | | | Before |
| 5/15/2012 | BRK | Varvaro | Demoted to reserve roster | | | Before |
| 5/15/2012 | CIO | Figgins | Demoted to reserve roster | | | Before |
| 5/15/2012 | CIO | Rhymes | Promoted to active roster | | | Before |
| 5/15/2012 | NYD | Morel | Promoted to active roster | | | Before |
| 5/15/2012 | NYD | Vitters | Demoted to reserve roster | | | Before |
| 5/16/2012 | FDH | Beachy | Placed on Injured List | | 5/16/2012 | Before |
| 5/16/2012 | FDH | Cashner | Promoted to active roster | | | Before |
| 5/16/2012 | HAR | Baker,Je | Demoted to reserve roster | | | Before |
| 5/16/2012 | HAR | Barmes | Promoted to active roster | | | Before |
| 5/16/2012 | HAR | Kipnis | Activated from Injured List | | | Before |
| 5/16/2012 | HAR | Samardzija | Promoted to active roster | | | Before |
| 5/16/2012 | HAR | Simmons | Demoted to reserve roster | | | Before |
| 5/16/2012 | HAR | Vincent | Placed on Injured List | | 5/16/2012 | Before |
| 5/16/2012 | NYD | Berken,J | Demoted to reserve roster | | | Before |
| 5/16/2012 | NYD | White | Promoted to active roster | | | Before |
| 5/18/2012 | CIO | Bard | Promoted to active roster | | | Before |
| 5/18/2012 | CIO | Noesi | Demoted to reserve roster | | | Before |
| 5/18/2012 | HHR | Baker,Jo | Placed on Injured List | | 5/16/2012 | Before |
| 5/18/2012 | HHR | Stewart,C | Promoted to active roster | | | Before |
| 5/19/2012 | CIO | Acosta | Demoted to reserve roster | | | Before |
| 5/19/2012 | CIO | Acosta | Promoted to active roster | | | Before |
| 5/19/2012 | CIO | Stewart,Z | Promoted to active roster | | | Before |
| 5/19/2012 | CIO | Volstad | Demoted to reserve roster | | | Before |
| 5/19/2012 | CIO | Wilk | Promoted to active roster | | | Before |
| 5/19/2012 | CIO | Wolf,R | Demoted to reserve roster | | | Before |
| 5/19/2012 | CSS | Blevins | Promoted to active roster | | | Before |
| 5/19/2012 | CSS | Cishek | Demoted to reserve roster | | | Before |
| 5/19/2012 | CSS | Cook,R | Demoted to reserve roster | | | Before |
| 5/19/2012 | CSS | Hanrahan | Demoted to reserve roster | | | Before |
| 5/19/2012 | CSS | Jeffress | Promoted to active roster | | | Before |
| 5/19/2012 | CSS | Jones,N | Promoted to active roster | | | Before |
| 5/20/2012 | CSS | Gonzalez,Mic | Released | | | Before |
| 5/20/2012 | CSS | Gonzalez,Mig | Signed | | | Before |
| 5/21/2012 | CIO | Hernandez,Ra | Demoted to reserve roster | | | Before |
| 5/21/2012 | CIO | Pena,B | Promoted to active roster | | | Before |
| 5/21/2012 | FDH | Cashner | Demoted to reserve roster | | | Before |
| 5/21/2012 | FDH | McHugh | Promoted to active roster | | | Before |
| 5/21/2012 | RMO | Fife | Demoted to reserve roster | | | Before |
| 5/21/2012 | RMO | Odorizzi | Activated from Injured List | | | Before |
| 5/22/2012 | ANN | Ackley | Promoted to active roster | | | Before |
| 5/22/2012 | ANN | Chatwood | Demoted to reserve roster | | | Before |
| 5/22/2012 | ANN | Gomes,Y | Demoted to reserve roster | | | Before |
| 5/22/2012 | ANN | Gregorius | Demoted to reserve roster | | | Before |
| 5/22/2012 | ANN | Hart | Promoted to active roster | | | Before |
| 5/22/2012 | ANN | Lindstrom | Promoted to active roster | | | Before |
| 5/22/2012 | CSS | Mauer | Demoted to reserve roster | | | Before |
| 5/22/2012 | CSS | Moore,S | Demoted to reserve roster | | | Before |
| 5/22/2012 | CSS | Ortiz | Activated from Injured List | | | Before |
| 5/22/2012 | CSS | Ruiz | Activated from Injured List | | | Before |
| 5/23/2012 | BRK | Bay | Placed on Injured List | | 5/22/2012 | Before |
| 5/23/2012 | BRK | Cuddyer | Activated from Injured List | | | Before |
| 5/23/2012 | CIO | Oswalt | Promoted to active roster | | | Before |
| 5/23/2012 | CIO | Stewart,Z | Demoted to reserve roster | | | Before |
| 5/23/2012 | RMO | Belisle | Promoted to active roster | | | Before |
| 5/23/2012 | RMO | Gallardo | Promoted to active roster | | | Before |
| 5/23/2012 | RMO | Hendriks | Placed on Injured List | | 5/21/2012 | Before |
| 5/23/2012 | RMO | Odorizzi | Demoted to reserve roster | | | Before |
| 5/25/2012 | BRK | Donald | Promoted to active roster | | | Before |
| 5/25/2012 | BRK | Martinez,M | Demoted to reserve roster | | | Before |
| 5/25/2012 | BRK | Nady | Demoted to reserve roster | | | Before |
| 5/25/2012 | BRK | Rivera,J | Promoted to active roster | | | Before |
| 5/25/2012 | CIO | Machado | Demoted to reserve roster | | | Before |
| 5/25/2012 | CIO | Ohlendorf | Promoted to active roster | | | Before |
| 5/25/2012 | CIO | Valencia,D | Promoted to active roster | | | Before |
| 5/25/2012 | CIO | Wilk | Demoted to reserve roster | | | Before |
| 5/27/2012 | HHR | Beavan | Demoted to reserve roster | | | Before |
| 5/27/2012 | HHR | McAllister | Promoted to active roster | | | Before |
| 5/27/2012 | NYD | Hand | Demoted to reserve roster | | | Before |
| 5/27/2012 | NYD | Reed | Promoted to active roster | | | Before |
| 5/29/2012 | RMO | Herrmann,C | Promoted to active roster | | | Before |
| 5/29/2012 | RMO | Schneider | Demoted to reserve roster | | | Before |
| 5/30/2012 | ANN | Marcum | Promoted to active roster | | | Before |
| 5/30/2012 | ANN | Nolasco | Placed on Injured List | | 5/29/2012 | Before |
| 5/30/2012 | CIO | Lincecum | Promoted to active roster | | | Before |
| 5/30/2012 | CIO | Ohlendorf | Demoted to reserve roster | | | Before |
| 5/30/2012 | CSS | Cishek | Promoted to active roster | | | Before |
| 5/30/2012 | CSS | Cook,R | Promoted to active roster | | | Before |
| 5/30/2012 | CSS | Price | Placed on Injured List | | 5/29/2012 | Before |
| 5/30/2012 | CSS | Ross,R | Demoted to reserve roster | | | Before |
| 5/30/2012 | NYD | Diekman | Demoted to reserve roster | | | Before |
| 5/30/2012 | NYD | Swarzak | Promoted to active roster | | | Before |
| 6/1/2012 | CIO | Bailey,A | Promoted to active roster | | | Before |
| 6/1/2012 | CIO | Keuchel | Demoted to reserve roster | | | Before |
| 6/1/2012 | CSS | McCarthy | Placed on Injured List | | 6/1/2012 | Before |
| 6/1/2012 | CSS | Paulino,F | Promoted to active roster | | | Before |
| 6/2/2012 | BRK | Humber | Placed on Injured List | | 6/2/2012 | Before |
| 6/2/2012 | BRK | Punto,N | Demoted to reserve roster | | | Before |
| 6/2/2012 | BRK | Villanueva | Promoted to active roster | | | Before |
| 6/2/2012 | BRK | Youkilis | Promoted to active roster | | | Before |
| 6/3/2012 | BRK | Parker,B | Demoted to reserve roster | | | Before |
| 6/3/2012 | BRK | Tomlin | Promoted to active roster | | | Before |
| 6/3/2012 | CSS | Blevins | Demoted to reserve roster | | | Before |
| 6/3/2012 | CSS | Cishek | Demoted to reserve roster | | | Before |
| 6/3/2012 | CSS | Delgado | Promoted to active roster | | | Before |
| 6/3/2012 | CSS | Thatcher | Promoted to active roster | | | Before |
| 6/4/2012 | NYD | Cairo | Demoted to reserve roster | | | Before |
| 6/4/2012 | NYD | Lee,Ca | Promoted to active roster | | | Before |
| 6/5/2012 | CSS | Hanrahan | Promoted to active roster | | | Before |
| 6/5/2012 | CSS | Jeffress | Demoted to reserve roster | | | Before |
| 6/6/2012 | NYD | Hundley | Promoted to active roster | | | Before |
| 6/6/2012 | NYD | Mesoraco | Demoted to reserve roster | | | Before |
| 6/6/2012 | SOI | Eveland | Promoted to active roster | | | Before |
| 6/6/2012 | SOI | Fuentes,B | Demoted to reserve roster | | | Before |
| 6/7/2012 | RMO | Gose | Demoted to reserve roster | | | Before |
| 6/7/2012 | RMO | Pelfrey | Promoted to active roster | | | Before |
| 6/7/2012 | RMO | Tillman | Demoted to reserve roster | | | Before |
| 6/7/2012 | RMO | Valdespin | Promoted to active roster | | | Before |
| 6/9/2012 | CIO | Bailey,A | Demoted to reserve roster | | | Before |
| 6/9/2012 | CIO | Sanchez,J | Demoted to reserve roster | | | Before |
| 6/9/2012 | CIO | Wang | Promoted to active roster | | | Before |
| 6/9/2012 | CIO | Wolf,R | Promoted to active roster | | | Before |
| 6/10/2012 | HAR | Carp | Promoted to active roster | | | Before |
| 6/10/2012 | HAR | Kipnis | Placed on Injured List | | 6/10/2012 | Before |
| 6/10/2012 | HAR | Kipnis | Placed on Injured List | | 6/10/2012 | Before |
| 6/10/2012 | RMO | Hendriks | Activated from Injured List | | | Before |
| 6/10/2012 | RMO | Hudson,T | Placed on Injured List | | 6/8/2012 | Before |
| 6/11/2012 | CIO | Lincecum | Demoted to reserve roster | | | Before |
| 6/11/2012 | CIO | Matsuzaka | Activated from Injured List | | | Before |
| 6/12/2012 | FDH | Burton | Promoted to active roster | | | Before |
| 6/12/2012 | FDH | Uehara | Demoted to reserve roster | | | Before |
| 6/13/2012 | CIO | Burriss | Promoted to active roster | | | Before |
| 6/13/2012 | CIO | Gordon,D | Demoted to reserve roster | | | Before |
| 6/14/2012 | FDH | Affeldt | Promoted to active roster | | | Before |
| 6/14/2012 | FDH | Blackley,T | Promoted to active roster | | | Before |
| 6/14/2012 | FDH | Boxberger | Demoted to reserve roster | | | Before |
| 6/14/2012 | FDH | McHugh | Demoted to reserve roster | | | Before |
| 6/15/2012 | ANN | Chisenhall | Demoted to reserve roster | | | Before |
| 6/15/2012 | ANN | Marcum | Demoted to reserve roster | | | Before |
| 6/15/2012 | ANN | Nolasco | Activated from Injured List | | | Before |
| 6/15/2012 | ANN | Roberts,R | Promoted to active roster | | | Before |
| 6/15/2012 | CSS | Delgado | Demoted to reserve roster | | | Before |
| 6/15/2012 | CSS | Price | Activated from Injured List | | | Before |
| 6/16/2012 | CSS | Cishek | Promoted to active roster | | | Before |
| 6/16/2012 | CSS | Jones,N | Demoted to reserve roster | | | Before |
| 6/16/2012 | FDH | Fontenot | Promoted to active roster | | | Before |
| 6/16/2012 | FDH | Votto | Placed on Injured List | | 6/16/2012 | Before |
| 6/16/2012 | SOI | Andino | Promoted to active roster | | | Before |
| 6/16/2012 | SOI | Matsui | Demoted to reserve roster | | | Before |
| 6/18/2012 | NYD | Galarraga | Demoted to reserve roster | | | Before |
| 6/18/2012 | NYD | Gregg | Promoted to active roster | | | Before |
| 6/19/2012 | ANN | Ackley | Demoted to reserve roster | | | Before |
| 6/19/2012 | ANN | Arencibia | Promoted to active roster | | | Before |
| 6/19/2012 | BRK | Bay | Activated from Injured List | | | Before |
| 6/19/2012 | BRK | Hinske | Demoted to reserve roster | | | Before |
| 6/21/2012 | BRK | Boesch | Promoted to active roster | | | Before |
| 6/21/2012 | BRK | Cuddyer | Placed on Injured List | | 6/20/2012 | Before |
| 6/21/2012 | CSS | Mauer | Promoted to active roster | | | Before |
| 6/21/2012 | CSS | Ruiz | Demoted to reserve roster | | | Before |
| 6/21/2012 | NYD | Conrad,B | Promoted to active roster | | | Before |
| 6/21/2012 | NYD | Morel | Demoted to reserve roster | | | Before |
| 6/22/2012 | CIO | Nickeas | Demoted to reserve roster | | | Before |
| 6/22/2012 | CIO | Sogard | Promoted to active roster | | | Before |
| 6/22/2012 | CIO | Soto,G | Promoted to active roster | | | Before |
| 6/22/2012 | CIO | Young,Mi | Demoted to reserve roster | | | Before |
| 6/24/2012 | CIO | Figgins | Promoted to active roster | | | Before |
| 6/24/2012 | CIO | Revere | Demoted to reserve roster | | | Before |
| 6/24/2012 | NYD | Rolen | Promoted to active roster | | | Before |
| 6/24/2012 | NYD | Rosales | Demoted to reserve roster | | | Before |
| 6/25/2012 | CIO | Cordero | Demoted to reserve roster | | | Before |
| 6/25/2012 | CIO | Jimenez,U | Promoted to active roster | | | Before |
| 6/25/2012 | HHR | Perez,M | Promoted to active roster | | | Before |
| 6/25/2012 | HHR | Pollock | Promoted to active roster | | | Before |
| 6/25/2012 | HHR | Smyly | Demoted to reserve roster | | | Before |
| 6/25/2012 | HHR | Venable | Placed on Injured List | | 6/25/2012 | Before |
| 6/27/2012 | ANN | Ackley | Promoted to active roster | | | Before |
| 6/27/2012 | ANN | Arencibia | Demoted to reserve roster | | | Before |
| 6/27/2012 | ANN | Joyce | Promoted to active roster | | | Before |
| 6/27/2012 | ANN | Werth | Placed on Injured List | | 6/26/2012 | Before |
| 6/27/2012 | BRK | Berkman | Promoted to active roster | | | Before |
| 6/27/2012 | BRK | Coke | Promoted to active roster | | | Before |
| 6/27/2012 | BRK | Dunn,M | Demoted to reserve roster | | | Before |
| 6/27/2012 | BRK | Vizquel | Demoted to reserve roster | | | Before |
| 6/27/2012 | RMO | Hendriks | Placed on Injured List | | 6/27/2012 | Before |
| 6/27/2012 | RMO | Hudson,T | Activated from Injured List | | | Before |
| 6/28/2012 | HAR | Carp | Demoted to reserve roster | | | Before |
| 6/28/2012 | HAR | Chacin | Demoted to reserve roster | | | Before |
| 6/28/2012 | HAR | Gutierrez | Promoted to active roster | | | Before |
| 6/28/2012 | HAR | Harris,WT | Promoted to active roster | | | Before |
| 6/28/2012 | HAR | Kipnis | Activated from Injured List | | | Before |
| 6/28/2012 | HAR | Nava | Activated from Injured List | | | Before |
| 6/28/2012 | HAR | Ottavino | Demoted to reserve roster | | | Before |
| 6/28/2012 | HAR | Pearce | Demoted to reserve roster | | | Before |
| 6/28/2012 | NYD | Chavez,J | Promoted to active roster | | | Before |
| 6/28/2012 | NYD | Marquis | Demoted to reserve roster | | | Before |
| 6/29/2012 | CIO | Lillibridge,B | Promoted to active roster | | | Before |
| 6/29/2012 | CIO | Petersen | Demoted to reserve roster | | | Before |
| 7/3/2012 | BRK | Humber | Activated from Injured List | | | Before |
| 7/3/2012 | BRK | Tolleson,Sh | Demoted to reserve roster | | | Before |
| 7/3/2012 | HAR | Laird,G | Placed on Injured List | | 6/30/2012 | Before |
| 7/3/2012 | HAR | Marson | Promoted to active roster | | | Before |
| 7/3/2012 | NYD | Jurrjens | Promoted to active roster | | | Before |
| 7/3/2012 | NYD | Smith,W | Demoted to reserve roster | | | Before |
| 7/4/2012 | CSS | Paulino,F | Demoted to reserve roster | | | Before |
| 7/4/2012 | CSS | Stults,E | Promoted to active roster | | | Before |
| 7/4/2012 | FDH | Beachy | Activated from Injured List | | | Before |
| 7/4/2012 | FDH | Blackley,T | Demoted to reserve roster | | | Before |
| 7/5/2012 | BRK | Boesch | Demoted to reserve roster | | | Before |
| 7/5/2012 | BRK | Cuddyer | Activated from Injured List | | | Before |
| 7/5/2012 | CIO | Wang | Demoted to reserve roster | | | Before |
| 7/6/2012 | CIO | Jimenez,U | Demoted to reserve roster | | | Before |
| 7/6/2012 | CIO | Lincecum | Promoted to active roster | | | Before |
| 7/6/2012 | CIO | Volstad | Promoted to active roster | | | Before |
| 7/6/2012 | NYD | Gearrin | Promoted to active roster | | | Before |
| 7/6/2012 | NYD | Swarzak | Placed on Injured List | | 7/6/2012 | Before |
| 7/6/2012 | RMO | Pelfrey | Placed on Injured List | | 7/5/2012 | Before |
| 7/8/2012 | CIO | Hernandez,Li | Demoted to reserve roster | | | Before |
| 7/8/2012 | CIO | Ohlendorf | Promoted to active roster | | | Before |
| 7/8/2012 | SOI | Eveland | Demoted to reserve roster | | | Before |
| 7/8/2012 | SOI | Snyder,C | Promoted to active roster | | | Before |
| 7/9/2012 | BRK | Hudson,O | Promoted to active roster | | | Before |
| 7/9/2012 | BRK | Straily | Demoted to reserve roster | | | Before |
| 7/9/2012 | RMO | Francis | Promoted to active roster | | | Before |
| 7/9/2012 | RMO | Gorzelanny | Demoted to reserve roster | | | Before |
| 7/9/2012 | RMO | Leake | Promoted to active roster | | | Before |
| 7/9/2012 | RMO | Lilly | Demoted to reserve roster | | | Before |
| 7/9/2012 | RMO | Luebke | Promoted to active roster | | | Before |
| 7/10/2012 | ANN | Ayala | Promoted to active roster | | | Before |
| 7/10/2012 | ANN | Street | Demoted to reserve roster | | | Before |
| 7/10/2012 | RMO | Bogusevic | Promoted to active roster | | | Before |
| 7/10/2012 | RMO | Garcia,A | Demoted to reserve roster | | | Before |
| 7/10/2012 | RMO | Herrmann,C | Demoted to reserve roster | | | Before |
| 7/10/2012 | RMO | McGehee | Demoted to reserve roster | | | Before |
| 7/10/2012 | RMO | Morrison | Demoted to reserve roster | | | Before |
| 7/10/2012 | RMO | Nix,J | Promoted to active roster | | | Before |
| 7/10/2012 | RMO | Paulino,R | Promoted to active roster | | | Before |
| 7/10/2012 | RMO | Wallace | Promoted to active roster | | | Before |
| 7/11/2012 | CIO | Carreno | Promoted to active roster | | | Before |
| 7/11/2012 | CIO | Lincecum | Demoted to reserve roster | | | Before |
| 7/11/2012 | CSS | Moore,S | Promoted to active roster | | | Before |
| 7/11/2012 | CSS | Ramirez,Ar | Placed on Injured List | | 7/11/2012 | Before |
| 7/11/2012 | CSS | Rodriguez,S | Promoted to active roster | | | Before |
| 7/11/2012 | CSS | Segura,J | Demoted to reserve roster | | | Before |
| 7/11/2012 | HHR | Cabrera,Ev | Placed on Injured List | | 7/11/2012 | Before |
| 7/11/2012 | HHR | Venable | Activated from Injured List | | | Before |
| 7/13/2012 | FDH | Villarreal,B | Acquired via trade | ALP | | After |
| 7/14/2012 | BRK | Andino | Acquired via trade | SOI | | After |
| 7/14/2012 | SOI | Andino | Traded away | BRK | | After |
| 7/15/2012 | SOI | Bastardo | Promoted to active roster | | | Before |
| 7/15/2012 | SOI | Casilla,S | Demoted to reserve roster | | | Before |
| 7/15/2012 | SOI | Chavez.En | Promoted to active roster | | | Before |
| 7/15/2012 | SOI | de la Rosa,J | Promoted to active roster | | | Before |
| 7/15/2012 | SOI | Dobbs | Demoted to reserve roster | | | Before |
| 7/15/2012 | SOI | Downs,S | Demoted to reserve roster | | | Before |
| 7/15/2012 | SOI | Mendoza | Promoted to active roster | | | Before |
| 7/15/2012 | SOI | Snyder,C | Demoted to reserve roster | | | Before |
| 7/15/2012 | SOI | Valverde | Demoted to reserve roster | | | Before |
| 7/15/2012 | SOI | Wigginton | Promoted to active roster | | | Before |
| 7/15/2012 | SOI | Young,CR | Promoted to active roster | | | Before |
| 7/16/2012 | BRK | Benoit | Demoted to reserve roster | | | Before |
| 7/16/2012 | BRK | Cruz,R | Promoted to active roster | | | Before |
| 7/16/2012 | BRK | Rivera,J | Placed on Injured List | | 7/16/2012 | Before |
| 7/16/2012 | HHR | Beavan | Promoted to active roster | | | Before |
| 7/16/2012 | HHR | Perez,M | Placed on Injured List | | 7/16/2012 | Before |
| 7/16/2012 | SOI | Kotchman | Promoted to active roster | | | Before |
| 7/16/2012 | SOI | Sandoval | Placed on Injured List | | 7/15/2012 | Before |
| 7/17/2012 | CIO | Oswalt | Demoted to reserve roster | | | Before |
| 7/19/2012 | CIO | Germano,J | Promoted to active roster | | | Before |
| 7/20/2012 | CSS | Buehrle | Placed on Injured List | | 7/18/2012 | Before |
| 7/20/2012 | CSS | Jeffress | Promoted to active roster | | | Before |
| 7/20/2012 | HAR | Baker,Je | Demoted to reserve roster | | | Before |
| 7/20/2012 | HAR | Brantly | Promoted to active roster | | | Before |
| 7/20/2012 | HAR | Carp | Promoted to active roster | | | Before |
| 7/20/2012 | HAR | Castro,J | Demoted to reserve roster | | | Before |
| 7/20/2012 | HAR | Davis,C | Placed on Injured List | | 7/18/2012 | Before |
| 7/20/2012 | HAR | Davis,C | Placed on Injured List | | 7/18/2012 | Before |
| 7/20/2012 | HAR | Holland,D | Demoted to reserve roster | | | Before |
| 7/20/2012 | HAR | Howell | Demoted to reserve roster | | | Before |
| 7/20/2012 | HAR | Kluber | Promoted to active roster | | | Before |
| 7/20/2012 | HAR | Melancon | Promoted to active roster | | | Before |
| 7/20/2012 | HAR | Ottavino | Promoted to active roster | | | Before |
| 7/20/2012 | HAR | Vincent | Demoted to reserve roster | | | Before |
| 7/20/2012 | HHR | Bernadina | Promoted to active roster | | | Before |
| 7/20/2012 | HHR | Harang | Placed on Injured List | | 7/18/2012 | Before |
| 7/20/2012 | HHR | Pierre | Placed on Injured List | | 7/18/2012 | Before |
| 7/20/2012 | HHR | Pollock | Demoted to reserve roster | | | Before |
| 7/20/2012 | HHR | Rogers,E | Promoted to active roster | | | Before |
| 7/20/2012 | HHR | Santiago,R | Promoted to active roster | | | Before |
| 7/20/2012 | HHR | Sweeney | Promoted to active roster | | | Before |
| 7/20/2012 | HHR | Walker | Placed on Injured List | | 7/18/2012 | Before |
| 7/21/2012 | CIO | Valdez,W | Demoted to reserve roster | | | Before |
| 7/21/2012 | CSS | Ortiz | Placed on Injured List | | 7/21/2012 | Before |
| 7/21/2012 | CSS | Ruiz | Promoted to active roster | | | Before |
| 7/21/2012 | NYD | Gearrin | Demoted to reserve roster | | | Before |
| 7/21/2012 | NYD | Swarzak | Activated from Injured List | | | Before |
| 7/21/2012 | SOI | Alburquerque | Promoted to active roster | | | Before |
| 7/21/2012 | SOI | Sabathia | Traded away | CEN | | After |
| 7/22/2012 | CIO | Figgins | Demoted to reserve roster | | | Before |
| 7/22/2012 | CIO | Young,D | Promoted to active roster | | | Before |
| 7/22/2012 | CIO | Young,Mi | Promoted to active roster | | | Before |
| 7/22/2012 | CIO | Campana | Acquired via trade | CSS | | After |
| 7/22/2012 | CIO | Petersen | Traded away | CSS | | After |
| 7/22/2012 | CSS | Jeffress | Demoted to reserve roster | | | Before |
| 7/22/2012 | CSS | Ross,R | Promoted to active roster | | | Before |
| 7/22/2012 | CSS | Campana | Traded away | CIO | | After |
| 7/22/2012 | CSS | Petersen | Acquired via trade | CIO | | After |
| 7/22/2012 | NYD | Reed | Traded away | ALP | | After |
| 7/22/2012 | NYD | Torres,An | Acquired via trade | ALP | | After |
| 7/22/2012 | NYD | Webb | Acquired via trade | ALP | | After |
| 7/23/2012 | BRK | Bay | Demoted to reserve roster | | | Before |
| 7/23/2012 | BRK | Boesch | Promoted to active roster | | | Before |
| 7/23/2012 | BRK | Clippard | Demoted to reserve roster | | | Before |
| 7/23/2012 | BRK | Halladay | Promoted to active roster | | | Before |
| 7/23/2012 | BRK | Kelly,J | Demoted to reserve roster | | | Before |
| 7/23/2012 | BRK | Straily | Promoted to active roster | | | Before |
| 7/23/2012 | HAR | Baker,Je | Promoted to active roster | | | Before |
| 7/23/2012 | HAR | Kipnis | Placed on Injured List | | 7/23/2012 | Before |
| 7/23/2012 | NYD | Bergesen | Promoted to active roster | | | Before |
| 7/23/2012 | NYD | Dolis | Demoted to reserve roster | | | Before |
| 7/23/2012 | RMO | Eovaldi | Demoted to reserve roster | | | Before |
| 7/23/2012 | RMO | Hendriks | Activated from Injured List | | | Before |
| 7/24/2012 | CIO | Campana | Promoted to active roster | | | Before |
| 7/24/2012 | CIO | Mather | Demoted to reserve roster | | | Before |
| 7/24/2012 | CSS | Blevins | Promoted to active roster | | | Before |
| 7/24/2012 | CSS | McCarthy | Activated from Injured List | | | Before |
| 7/24/2012 | CSS | Ross,R | Demoted to reserve roster | | | Before |
| 7/24/2012 | CSS | Smith,J | Demoted to reserve roster | | | Before |
| 7/24/2012 | FDH | Beachy | Demoted to reserve roster | | | Before |
| 7/24/2012 | FDH | Blackley,T | Promoted to active roster | | | Before |
| 7/24/2012 | FDH | Doolittle | Demoted to reserve roster | | | Before |
| 7/24/2012 | FDH | Villarreal,B | Promoted to active roster | | | Before |
| 7/25/2012 | CIO | Bard | Demoted to reserve roster | | | Before |
| 7/25/2012 | CIO | Wilk | Promoted to active roster | | | Before |
| 7/25/2012 | FDH | Fontenot | Demoted to reserve roster | | | Before |
| 7/25/2012 | FDH | Wilson,Bo | Promoted to active roster | | | Before |
| 7/25/2012 | NYD | Conrad,B | Demoted to reserve roster | | | Before |
| 7/25/2012 | NYD | Nunez | Promoted to active roster | | | Before |
| 7/25/2012 | NYD | Thames | Demoted to reserve roster | | | Before |
| 7/25/2012 | NYD | Torres,An | Promoted to active roster | | | Before |
| 7/26/2012 | HHR | Cabrera,Ev | Activated from Injured List | | | Before |
| 7/26/2012 | HHR | Frazier | Demoted to reserve roster | | | Before |
| 7/26/2012 | NYD | Hayes | Demoted to reserve roster | | | Before |
| 7/26/2012 | NYD | Treanor | Promoted to active roster | | | Before |
| 7/26/2012 | RMO | Kontos | Promoted to active roster | | | Before |
| 7/26/2012 | RMO | McGehee | Promoted to active roster | | | Before |
| 7/26/2012 | RMO | Tejada | Placed on Injured List | | 7/26/2012 | Before |
| 7/26/2012 | RMO | Hester | Acquired via trade | CTW | | After |
| 7/26/2012 | RMO | Hudson,T | Traded away | CTW | | After |
| 7/26/2012 | RMO | Kontos | Acquired via trade | CTW | | After |
| 7/27/2012 | CIO | Lavarnway | Promoted to active roster | | | Before |
| 7/27/2012 | CIO | Soto,G | Demoted to reserve roster | | | Before |
| 7/27/2012 | CSS | Hairston,J | Demoted to reserve roster | | | Before |
| 7/27/2012 | CSS | Ramirez,Ar | Activated from Injured List | | | Before |
| 7/28/2012 | ANN | Ackley | Demoted to reserve roster | | | Before |
| 7/28/2012 | ANN | Arencibia | Promoted to active roster | | | Before |
| 7/28/2012 | ANN | Ross,D | Demoted to reserve roster | | | Before |
| 7/28/2012 | ANN | Werth | Activated from Injured List | | | Before |
| 7/28/2012 | FDH | Lalli | Promoted to active roster | | | Before |
| 7/28/2012 | FDH | Ramos,W | Demoted to reserve roster | | | Before |
| 7/29/2012 | BRK | Moscoso | Promoted to active roster | | | Before |
| 7/29/2012 | BRK | Villanueva | Placed on Injured List | | 7/29/2012 | Before |
| 7/29/2012 | CIO | Matsuzaka | Demoted to reserve roster | | | Before |
| 7/29/2012 | CIO | Stewart,Z | Promoted to active roster | | | Before |
| 7/30/2012 | FDH | Fontenot | Promoted to active roster | | | Before |
| 7/30/2012 | FDH | Lalli | Demoted to reserve roster | | | Before |
| 7/30/2012 | HAR | Barmes | Demoted to reserve roster | | | Before |
| 7/30/2012 | HAR | Gentry | Demoted to reserve roster | | | Before |
| 7/30/2012 | HAR | Herrmann,F | Promoted to active roster | | | Before |
| 7/30/2012 | HAR | Kluber | Demoted to reserve roster | | | Before |
| 7/30/2012 | HAR | Mercer | Promoted to active roster | | | Before |
| 7/30/2012 | HAR | Pearce | Promoted to active roster | | | Before |
| 7/30/2012 | NYD | Chavez,J | Demoted to reserve roster | | | Before |
| 7/30/2012 | NYD | Nicasio | Promoted to active roster | | | Before |
| 7/30/2012 | SOI | Kotchman | Demoted to reserve roster | | | Before |
| 7/30/2012 | SOI | Sandoval | Activated from Injured List | | | Before |
| 7/31/2012 | ANN | Ackley | Traded away | BRK | | After |
| 7/31/2012 | BRK | Ackley | Acquired via trade | ANN | | After |
| 7/31/2012 | BRK | Clevenger | Acquired via trade | TEW | | After |
| 7/31/2012 | BRK | Cuddyer | Traded away | TEW | | After |
| 7/31/2012 | BRK | Hairston,S | Traded away | NYD | | After |
| 7/31/2012 | BRK | Johnson,E | Acquired via trade | CIN | | After |
| 7/31/2012 | BRK | Vitters | Acquired via trade | NYD | | After |
| 7/31/2012 | BRK | Youkilis | Traded away | TEW | | After |
| 7/31/2012 | CIO | Lincecum | Promoted to active roster | | | Before |
| 7/31/2012 | CIO | Ohlendorf | Demoted to reserve roster | | | Before |
| 7/31/2012 | CSS | Moore,S | Demoted to reserve roster | | | Before |
| 7/31/2012 | CSS | Segura,J | Promoted to active roster | | | Before |
| 7/31/2012 | CSS | Logan | Acquired via trade | HHR | | After |
| 7/31/2012 | HHR | Logan | Traded away | CSS | | After |
| 7/31/2012 | NYD | Burnett,S | Acquired via trade | CTW | | After |
| 7/31/2012 | NYD | Galarraga | Traded away | CTW | | After |
| 7/31/2012 | NYD | Hairston,S | Acquired via trade | BRK | | After |
| 7/31/2012 | NYD | Vitters | Traded away | BRK | | After |
| 7/31/2012 | RMO | Greene,Ty | Acquired via trade | CTW | | After |
| 8/1/2012 | BRK | Ackley | Promoted to active roster | | | Before |
| 8/1/2012 | BRK | Bay | Promoted to active roster | | | Before |
| 8/1/2012 | BRK | Berkman | Demoted to reserve roster | | | Before |
| 8/1/2012 | BRK | Clevenger | Promoted to active roster | | | Before |
| 8/1/2012 | BRK | Donald | Demoted to reserve roster | | | Before |
| 8/1/2012 | BRK | Johnson,E | Promoted to active roster | | | Before |
| 8/1/2012 | BRK | Punto,N | Promoted to active roster | | | Before |
| 8/1/2012 | BRK | Straily | Demoted to reserve roster | | | Before |
| 8/1/2012 | CIO | Blackburn | Demoted to reserve roster | | | Before |
| 8/1/2012 | CIO | Jimenez,U | Promoted to active roster | | | Before |
| 8/1/2012 | CSS | Logan | Demoted to reserve roster | | | Before |
| 8/1/2012 | HHR | Beavan | Demoted to reserve roster | | | Before |
| 8/1/2012 | HHR | Perez,M | Activated from Injured List | | | Before |
| 8/1/2012 | HHR | Venters | Promoted to active roster | | | Before |
| 8/2/2012 | FDH | Cruz,L | Demoted to reserve roster | | | Before |
| 8/2/2012 | FDH | Votto | Activated from Injured List | | | Before |
| 8/4/2012 | CSS | Buehrle | Activated from Injured List | | | Before |
| 8/4/2012 | CSS | Stults,E | Demoted to reserve roster | | | Before |
| 8/4/2012 | FDH | Turner,Ja | Promoted to active roster | | | Before |
| 8/4/2012 | RMO | Cowgill | Demoted to reserve roster | | | Before |
| 8/4/2012 | RMO | Gose | Promoted to active roster | | | Before |
| 8/4/2012 | RMO | Greene,Ty | Promoted to active roster | | | Before |
| 8/4/2012 | RMO | Hendriks | Demoted to reserve roster | | | Before |
| 8/4/2012 | RMO | Pelfrey | Activated from Injured List | | | Before |
| 8/4/2012 | RMO | Pelfrey | Demoted to reserve roster | | | Before |
| 8/5/2012 | BRK | Punto,N | Demoted to reserve roster | | | Before |
| 8/5/2012 | BRK | Rivera,J | Activated from Injured List | | | Before |
| 8/5/2012 | CIO | Butera | Promoted to active roster | | | Before |
| 8/5/2012 | CIO | Wilk | Demoted to reserve roster | | | Before |
| 8/5/2012 | HAR | Baker,Je | Demoted to reserve roster | | | Before |
| 8/5/2012 | HAR | Simmons | Promoted to active roster | | | Before |
| 8/6/2012 | ANN | Robertson,D | Demoted to reserve roster | | | Before |
| 8/6/2012 | CIO | Campana | Demoted to reserve roster | | | Before |
| 8/6/2012 | CIO | Lavarnway | Demoted to reserve roster | | | Before |
| 8/6/2012 | CIO | Noesi | Promoted to active roster | | | Before |
| 8/6/2012 | CIO | Revere | Promoted to active roster | | | Before |
| 8/6/2012 | SOI | Alburquerque | Demoted to reserve roster | | | Before |
| 8/6/2012 | SOI | Warren | Promoted to active roster | | | Before |
| 8/7/2012 | CIO | Carreno | Demoted to reserve roster | | | Before |
| 8/7/2012 | CIO | Doubront | Promoted to active roster | | | Before |
| 8/7/2012 | CIO | Keuchel | Promoted to active roster | | | Before |
| 8/7/2012 | CIO | Stewart,Z | Demoted to reserve roster | | | Before |
| 8/7/2012 | CSS | Cain,L | Placed on Injured List | | 8/7/2012 | Before |
| 8/7/2012 | CSS | Ortiz | Activated from Injured List | | | Before |
| 8/8/2012 | ANN | Grilli | Promoted to active roster | | | Before |
| 8/8/2012 | ANN | League,B | Promoted to active roster | | | Before |
| 8/8/2012 | ANN | Mujica | Demoted to reserve roster | | | Before |
| 8/8/2012 | FDH | Cashner | Promoted to active roster | | | Before |
| 8/8/2012 | FDH | Strasburg | Placed on Injured List | | 8/8/2012 | Before |
| 8/9/2012 | HAR | Brantly | Placed on Injured List | | 8/8/2012 | Before |
| 8/9/2012 | HAR | Davis,C | Activated from Injured List | | | Before |
| 8/9/2012 | HAR | Kipnis | Activated from Injured List | | | Before |
| 8/9/2012 | HAR | Laird,G | Activated from Injured List | | | Before |
| 8/9/2012 | NYD | Pena,R | Promoted to active roster | | | Before |
| 8/9/2012 | NYD | Rolen | Placed on Injured List | | 8/9/2012 | Before |
| 8/9/2012 | SOI | Eveland | Promoted to active roster | | | Before |
| 8/9/2012 | SOI | Hellickson | Demoted to reserve roster | | | Before |
| 8/10/2012 | RMO | Cedeno,X | Promoted to active roster | | | Before |
| 8/10/2012 | RMO | Kendrick,K | Promoted to active roster | | | Before |
| 8/10/2012 | RMO | Pomeranz,D | Demoted to reserve roster | | | Before |
| 8/10/2012 | RMO | Rodriguez,Fr | Demoted to reserve roster | | | Before |
| 8/11/2012 | FDH | Anderson,BD | Promoted to active roster | | | Before |
| 8/11/2012 | FDH | Wilson,Bo | Placed on Injured List | | 8/11/2012 | Before |
| 8/11/2012 | HAR | Harris,WT | Demoted to reserve roster | | | Before |
| 8/11/2012 | HAR | Howell | Promoted to active roster | | | Before |
| 8/11/2012 | HHR | Harang | Activated from Injured List | | | Before |
| 8/11/2012 | HHR | LeBlanc | Demoted to reserve roster | | | Before |
| 8/11/2012 | HHR | Moustakas | Demoted to reserve roster | | | Before |
| 8/11/2012 | HHR | Walker | Activated from Injured List | | | Before |
| 8/11/2012 | NYD | Hairston,S | Promoted to active roster | | | Before |
| 8/11/2012 | NYD | Pena,R | Demoted to reserve roster | | | Before |
| 8/11/2012 | SOI | Warren | Placed on Injured List | | 8/11/2012 | Before |
| 8/12/2012 | HHR | Moustakas | Promoted to active roster | | | Before |
| 8/12/2012 | HHR | Walker | Placed on Injured List | | 8/12/2012 | Before |
| 8/12/2012 | SOI | Hernandez,G | Promoted to active roster | | | Before |
| 8/12/2012 | SOI | Kotchman | Promoted to active roster | | | Before |
| 8/12/2012 | SOI | Suzuki,I | Demoted to reserve roster | | | Before |
| 8/13/2012 | BRK | Cruz,R | Demoted to reserve roster | | | Before |
| 8/13/2012 | BRK | Villanueva | Activated from Injured List | | | Before |
| 8/13/2012 | CIO | Burriss | Demoted to reserve roster | | | Before |
| 8/13/2012 | CIO | Gordon,D | Promoted to active roster | | | Before |
| 8/13/2012 | CIO | Hernandez,Ra | Promoted to active roster | | | Before |
| 8/13/2012 | CIO | Pena,B | Demoted to reserve roster | | | Before |
| 8/13/2012 | CSS | Braun | Placed on Injured List | | 8/13/2012 | Before |
| 8/13/2012 | CSS | Moore,S | Promoted to active roster | | | Before |
| 8/14/2012 | CSS | Gonzalez,Mig | Demoted to reserve roster | | | Before |
| 8/14/2012 | CSS | Smith,J | Promoted to active roster | | | Before |
| 8/15/2012 | BRK | Marte,V | Promoted to active roster | | | Before |
| 8/15/2012 | BRK | Moscoso | Placed on Injured List | | 8/15/2012 | Before |
| 8/15/2012 | HHR | LeMahieu | Placed on Injured List | | 8/12/2012 | Before |
| 8/15/2012 | HHR | Podsednik | Promoted to active roster | | | Before |
| 8/16/2012 | CIO | Keuchel | Placed on Injured List | | 8/16/2012 | Before |
| 8/16/2012 | CIO | Sanchez,J | Promoted to active roster | | | Before |
| 8/17/2012 | SOI | Cook,A | Demoted to reserve roster | | | Before |
| 8/17/2012 | SOI | de la Rosa,J | Demoted to reserve roster | | | Before |
| 8/18/2012 | SOI | Downs,S | Promoted to active roster | | | Before |
| 8/18/2012 | SOI | Eveland | Demoted to reserve roster | | | Before |
| 8/18/2012 | SOI | Lidge | Promoted to active roster | | | Before |
| 8/18/2012 | SOI | Penny | Promoted to active roster | | | Before |
| 8/20/2012 | CSS | Blevins | Demoted to reserve roster | | | Before |
| 8/20/2012 | CSS | Hanrahan | Demoted to reserve roster | | | Before |
| 8/20/2012 | CSS | Jeffress | Promoted to active roster | | | Before |
| 8/20/2012 | CSS | Logan | Promoted to active roster | | | Before |
| 8/20/2012 | CSS | Putz | Demoted to reserve roster | | | Before |
| 8/20/2012 | CSS | Stults,E | Promoted to active roster | | | Before |
| 8/20/2012 | FDH | Turner,Ja | Demoted to reserve roster | | | Before |
| 8/20/2012 | HHR | Carroll,J | Placed on Injured List | | 8/18/2012 | Before |
| 8/20/2012 | HHR | Pierre | Activated from Injured List | | | Before |
| 8/20/2012 | SOI | Pence | Demoted to reserve roster | | | Before |
| 8/20/2012 | SOI | Smoak | Promoted to active roster | | | Before |
| 8/21/2012 | CIO | Machado | Promoted to active roster | | | Before |
| 8/21/2012 | CIO | Valencia,D | Demoted to reserve roster | | | Before |
| 8/21/2012 | HHR | Beavan | Promoted to active roster | | | Before |
| 8/21/2012 | HHR | Perez,M | Demoted to reserve roster | | | Before |
| 8/21/2012 | NYD | Johnson,D | Promoted to active roster | | | Before |
| 8/21/2012 | NYD | Lyles | Demoted to reserve roster | | | Before |
| 8/21/2012 | RMO | Cowgill | Promoted to active roster | | | Before |
| 8/21/2012 | RMO | Drew | Demoted to reserve roster | | | Before |
| 8/21/2012 | RMO | Gose | Demoted to reserve roster | | | Before |
| 8/21/2012 | RMO | Hendriks | Promoted to active roster | | | Before |
| 8/21/2012 | RMO | Luebke | Demoted to reserve roster | | | Before |
| 8/21/2012 | RMO | Tejada | Activated from Injured List | | | Before |
| 8/22/2012 | CIO | Hernandez,Ra | Placed on Injured List | | 8/22/2012 | Before |
| 8/22/2012 | CIO | Soto,G | Promoted to active roster | | | Before |
| 8/22/2012 | SOI | Penny | Demoted to reserve roster | | | Before |
| 8/23/2012 | CSS | Jeffress | Demoted to reserve roster | | | Before |
| 8/23/2012 | CSS | Putz | Promoted to active roster | | | Before |
| 8/23/2012 | FDH | Cashner | Demoted to reserve roster | | | Before |
| 8/23/2012 | FDH | Hamels | Demoted to reserve roster | | | Before |
| 8/23/2012 | FDH | Strasburg | Activated from Injured List | | | Before |
| 8/23/2012 | FDH | Turner,Ja | Promoted to active roster | | | Before |
| 8/23/2012 | SOI | Bourgeois | Promoted to active roster | | | Before |
| 8/23/2012 | SOI | Casilla,S | Promoted to active roster | | | Before |
| 8/23/2012 | SOI | Downs,S | Demoted to reserve roster | | | Before |
| 8/23/2012 | SOI | Fuentes,B | Promoted to active roster | | | Before |
| 8/23/2012 | SOI | Granderson | Demoted to reserve roster | | | Before |
| 8/23/2012 | SOI | Lidge | Demoted to reserve roster | | | Before |
| 8/23/2012 | SOI | Valverde | Promoted to active roster | | | Before |
| 8/24/2012 | SOI | Fuentes,B | Demoted to reserve roster | | | Before |
| 8/24/2012 | SOI | Hellickson | Promoted to active roster | | | Before |
| 8/25/2012 | BRK | Leon | Activated from Injured List | | | Before |
| 8/25/2012 | BRK | Morgan | Demoted to reserve roster | | | Before |
| 8/25/2012 | CIO | Campana | Promoted to active roster | | | Before |
| 8/25/2012 | CIO | Coghlan | Demoted to reserve roster | | | Before |
| 8/25/2012 | CSS | Delgado | Promoted to active roster | | | Before |
| 8/25/2012 | CSS | McCarthy | Demoted to reserve roster | | | Before |
| 8/26/2012 | NYD | Albers | Demoted to reserve roster | | | Before |
| 8/26/2012 | NYD | Burnett,S | Promoted to active roster | | | Before |
| 8/26/2012 | NYD | Correia | Demoted to reserve roster | | | Before |
| 8/26/2012 | NYD | Gearrin | Promoted to active roster | | | Before |
| 8/27/2012 | HHR | Baker,Jo | Activated from Injured List | | | Before |
| 8/27/2012 | HHR | Blanco,G | Demoted to reserve roster | | | Before |
| 8/27/2012 | HHR | Frazier | Promoted to active roster | | | Before |
| 8/27/2012 | HHR | LeMahieu | Activated from Injured List | | | Before |
| 8/27/2012 | HHR | Pierzynski | Demoted to reserve roster | | | Before |
| 8/27/2012 | HHR | Podsednik | Demoted to reserve roster | | | Before |
| 8/27/2012 | HHR | Venable | Demoted to reserve roster | | | Before |
| 8/27/2012 | HHR | Walker | Activated from Injured List | | | Before |
| 8/28/2012 | CIO | Acosta | Demoted to reserve roster | | | Before |
| 8/28/2012 | CIO | Bailey,A | Promoted to active roster | | | Before |
| 8/28/2012 | CSS | Braun | Activated from Injured List | | | Before |
| 8/28/2012 | CSS | Moore,S | Demoted to reserve roster | | | Before |
| 8/31/2012 | NYD | Bergesen | Demoted to reserve roster | | | Before |
| 8/31/2012 | NYD | Correia | Promoted to active roster | | | Before |
| 8/31/2012 | NYD | Gregg | Demoted to reserve roster | | | Before |
| 8/31/2012 | NYD | Lyles | Promoted to active roster | | | Before |
| 8/31/2012 | NYD | Marquis | Promoted to active roster | | | Before |
| 8/31/2012 | NYD | Morton | Demoted to reserve roster | | | Before |
| 9/1/2012 | CIO | Bailey,A | Demoted to reserve roster | | | Before |
| 9/1/2012 | CIO | Keuchel | Activated from Injured List | | | Before |
| 9/1/2012 | CSS | Ortiz | Demoted to reserve roster | | | Before |
| 9/1/2012 | FDH | Cruz,L | Promoted to active roster | | | Before |
| 9/1/2012 | FDH | Doolittle | Promoted to active roster | | | Before |
| 9/1/2012 | FDH | Falu | Promoted to active roster | | | Before |
| 9/1/2012 | FDH | Helton | Promoted to active roster | | | Before |
| 9/1/2012 | FDH | Salas | Promoted to active roster | | | Before |
| 9/2/2012 | CIO | Mather | Promoted to active roster | | | Before |
| 9/2/2012 | HHR | Blanco,G | Promoted to active roster | | | Before |
| 9/2/2012 | HHR | Capps,M | Promoted to active roster | | | Before |
| 9/2/2012 | HHR | Carroll,J | Activated from Injured List | | | Before |
| 9/2/2012 | HHR | Johnson,Ro | Promoted to active roster | | | Before |
| 9/2/2012 | HHR | LeBlanc | Promoted to active roster | | | Before |
| 9/2/2012 | HHR | Myers,B | Promoted to active roster | | | Before |
| 9/2/2012 | HHR | Perez,M | Promoted to active roster | | | Before |
| 9/2/2012 | HHR | Pierzynski | Promoted to active roster | | | Before |
| 9/2/2012 | HHR | Podsednik | Promoted to active roster | | | Before |
| 9/2/2012 | HHR | Pollock | Promoted to active roster | | | Before |
| 9/2/2012 | HHR | Rosenthal | Promoted to active roster | | | Before |
| 9/2/2012 | HHR | Smyly | Promoted to active roster | | | Before |
| 9/2/2012 | HHR | Venable | Promoted to active roster | | | Before |
| 9/2/2012 | SOI | Casilla,A | Promoted to active roster | | | Before |
| 9/2/2012 | SOI | Dobbs | Promoted to active roster | | | Before |
| 9/2/2012 | SOI | Izturis,M | Promoted to active roster | | | Before |
| 9/2/2012 | SOI | Matsui | Promoted to active roster | | | Before |
| 9/2/2012 | SOI | Murphy,DT | Demoted to reserve roster | | | Before |
| 9/2/2012 | SOI | Pastornicky | Promoted to active roster | | | Before |
| 9/2/2012 | SOI | Peralta,Jh | Demoted to reserve roster | | | Before |
| 9/2/2012 | SOI | Sandoval | Demoted to reserve roster | | | Before |
| 9/2/2012 | SOI | Snyder,C | Promoted to active roster | | | Before |
| 9/2/2012 | SOI | Torrealba,Y | Promoted to active roster | | | Before |
| 9/3/2012 | BRK | Hill,K | Promoted to active roster | | | Before |
| 9/3/2012 | BRK | Whiteside | Promoted to active roster | | | Before |
| 9/3/2012 | CSS | Cain,L | Activated from Injured List | | | Before |
| 9/3/2012 | CSS | Hairston,J | Promoted to active roster | | | Before |
| 9/3/2012 | CSS | Hanrahan | Promoted to active roster | | | Before |
| 9/3/2012 | CSS | Moore,S | Promoted to active roster | | | Before |
| 9/4/2012 | ANN | Lindstrom | Demoted to reserve roster | | | Before |
| 9/4/2012 | HAR | Baker,Je | Promoted to active roster | | | Before |
| 9/4/2012 | HAR | Brantly | Promoted to active roster | | | Before |
| 9/4/2012 | HAR | Carp | Promoted to active roster | | | Before |
| 9/4/2012 | HAR | Castro,J | Promoted to active roster | | | Before |
| 9/4/2012 | HAR | De La Rosa,D | Promoted to active roster | | | Before |
| 9/4/2012 | HAR | Eaton | Promoted to active roster | | | Before |
| 9/4/2012 | HAR | Gentry | Promoted to active roster | | | Before |
| 9/4/2012 | HAR | Harris,WT | Promoted to active roster | | | Before |
| 9/4/2012 | HAR | Holland,D | Promoted to active roster | | | Before |
| 9/4/2012 | HAR | Kintzler | Promoted to active roster | | | Before |
| 9/4/2012 | HAR | Kluber | Promoted to active roster | | | Before |
| 9/4/2012 | HAR | Mercer | Promoted to active roster | | | Before |
| 9/4/2012 | HAR | Navarro,D | Demoted to reserve roster | | | Before |
| 9/4/2012 | HAR | Navarro,D | Promoted to active roster | | | Before |
| 9/4/2012 | HAR | Parra,G | Promoted to active roster | | | Before |
| 9/4/2012 | HAR | Simmons | Promoted to active roster | | | Before |
| 9/4/2012 | HAR | Vincent | Promoted to active roster | | | Before |
| 9/5/2012 | ANN | Papelbon | Demoted to reserve roster | | | Before |
| 9/5/2012 | BRK | Cruz,R | Promoted to active roster | | | Before |
| 9/5/2012 | BRK | Donald | Promoted to active roster | | | Before |
| 9/5/2012 | BRK | Dunn,M | Promoted to active roster | | | Before |
| 9/5/2012 | BRK | Kelly,D | Promoted to active roster | | | Before |
| 9/5/2012 | BRK | Kelly,J | Promoted to active roster | | | Before |
| 9/5/2012 | BRK | Moscoso | Activated from Injured List | | | Before |
| 9/5/2012 | BRK | Punto,N | Promoted to active roster | | | Before |
| 9/5/2012 | BRK | Straily | Promoted to active roster | | | Before |
| 9/5/2012 | BRK | Vizquel | Promoted to active roster | | | Before |
| 9/5/2012 | CIO | Sanchez,J | Demoted to reserve roster | | | Before |
| 9/5/2012 | CIO | Stewart,Z | Promoted to active roster | | | Before |
| 9/6/2012 | CIO | Coghlan | Promoted to active roster | | | Before |
| 9/6/2012 | CIO | Escobar,E | Demoted to reserve roster | | | Before |
| 9/6/2012 | CSS | Galvis | Promoted to active roster | | | Before |
| 9/6/2012 | CSS | Jones,N | Promoted to active roster | | | Before |
| 9/6/2012 | CSS | Stults,E | Demoted to reserve roster | | | Before |
| 9/6/2012 | CSS | Utley | Demoted to reserve roster | | | Before |
| 9/7/2012 | ANN | Atchison | Promoted to active roster | | | Before |
| 9/7/2012 | ANN | Hafner | Promoted to active roster | | | Before |
| 9/7/2012 | ANN | Johnson,K | Promoted to active roster | | | Before |
| 9/7/2012 | ANN | Quintero | Promoted to active roster | | | Before |
| 9/7/2012 | ANN | Saunders,J | Promoted to active roster | | | Before |
| 9/7/2012 | FDH | Blackley,T | Demoted to reserve roster | | | Before |
| 9/7/2012 | FDH | Hamels | Promoted to active roster | | | Before |
| 9/9/2012 | HAR | Melancon | Demoted to reserve roster | | | Before |
| 9/10/2012 | ANN | Rodriguez,W | Demoted to reserve roster | | | Before |
| 9/10/2012 | BRK | Leon | Demoted to reserve roster | | | Before |
| 9/10/2012 | CIO | Grimm | Promoted to active roster | | | Before |
| 9/10/2012 | FDH | Beachy | Promoted to active roster | | | Before |
| 9/10/2012 | HAR | Herrmann,F | Demoted to reserve roster | | | Before |
| 9/10/2012 | HHR | Perez,M | Demoted to reserve roster | | | Before |
| 9/12/2012 | BRK | Donald | Demoted to reserve roster | | | Before |
| 9/12/2012 | BRK | Punto,N | Demoted to reserve roster | | | Before |
| 9/12/2012 | CIO | Burriss | Promoted to active roster | | | Before |
| 9/12/2012 | CIO | Cordero | Promoted to active roster | | | Before |
| 9/12/2012 | CIO | Hudson,D | Promoted to active roster | | | Before |
| 9/12/2012 | FDH | Anderson,BD | Demoted to reserve roster | | | Before |
| 9/12/2012 | HAR | Harris,WT | Demoted to reserve roster | | | Before |
| 9/12/2012 | HAR | Sale | Demoted to reserve roster | | | Before |
| 9/12/2012 | NYD | Diekman | Promoted to active roster | | | Before |
| 9/12/2012 | NYD | Nunez | Demoted to reserve roster | | | Before |
| 9/12/2012 | NYD | Rolen | Activated from Injured List | | | Before |
| 9/12/2012 | NYD | Wilson,Ja | Demoted to reserve roster | | | Before |
| 9/13/2012 | ANN | Chatwood | Promoted to active roster | | | Before |
| 9/13/2012 | ANN | Garcia,J | Promoted to active roster | | | Before |
| 9/13/2012 | ANN | Gomes,Y | Promoted to active roster | | | Before |
| 9/13/2012 | ANN | Greinke | Demoted to reserve roster | | | Before |
| 9/13/2012 | ANN | Marcum | Promoted to active roster | | | Before |
| 9/13/2012 | ANN | Mayberry | Promoted to active roster | | | Before |
| 9/13/2012 | ANN | Nolasco | Demoted to reserve roster | | | Before |
| 9/13/2012 | ANN | Ross,D | Promoted to active roster | | | Before |
| 9/13/2012 | ANN | Shields | Demoted to reserve roster | | | Before |
| 9/13/2012 | ANN | Westbrook | Promoted to active roster | | | Before |
| 9/13/2012 | ANN | Worley | Promoted to active roster | | | Before |
| 9/13/2012 | SOI | Avila | Demoted to reserve roster | | | Before |
| 9/14/2012 | FDH | Beachy | Demoted to reserve roster | | | Before |
| 9/14/2012 | NYD | Blackmon | Promoted to active roster | | | Before |
| 9/14/2012 | NYD | Conger | Promoted to active roster | | | Before |
| 9/14/2012 | NYD | Gregg | Promoted to active roster | | | Before |
| 9/14/2012 | NYD | Mesoraco | Promoted to active roster | | | Before |
| 9/14/2012 | NYD | Morton | Promoted to active roster | | | Before |
| 9/14/2012 | NYD | Wilson,Ja | Promoted to active roster | | | Before |
| 9/14/2012 | RMO | Exposito | Promoted to active roster | | | Before |
| 9/14/2012 | RMO | Hechavarria | Demoted to reserve roster | | | Before |
| 9/14/2012 | RMO | Hester | Promoted to active roster | | | Before |
| 9/15/2012 | CIO | Burriss | Demoted to reserve roster | | | Before |
| 9/15/2012 | CIO | Hernandez,Ra | Activated from Injured List | | | Before |
| 9/15/2012 | CIO | Raburn | Demoted to reserve roster | | | Before |
| 9/15/2012 | CIO | Sogard | Demoted to reserve roster | | | Before |
| 9/16/2012 | CIO | Grimm | Demoted to reserve roster | | | Before |
| 9/16/2012 | FDH | Wilson,Bo | Activated from Injured List | | | Before |
| 9/16/2012 | SOI | Warren | Activated from Injured List | | | Before |
| 9/16/2012 | SOI | Warren | Demoted to reserve roster | | | Before |
| 9/17/2012 | BRK | Bay | Demoted to reserve roster | | | Before |
| 9/17/2012 | CIO | Lillibridge,B | Demoted to reserve roster | | | Before |
| 9/17/2012 | CIO | Mather | Demoted to reserve roster | | | Before |
| 9/17/2012 | CIO | Nickeas | Promoted to active roster | | | Before |
| 9/17/2012 | CIO | Raburn | Promoted to active roster | | | Before |
| 9/17/2012 | CIO | Rhymes | Demoted to reserve roster | | | Before |
| 9/17/2012 | CIO | Stewart,Z | Demoted to reserve roster | | | Before |
| 9/17/2012 | CIO | Wang | Promoted to active roster | | | Before |
| 9/17/2012 | CSS | McCarthy | Promoted to active roster | | | Before |
| 9/17/2012 | SOI | Casilla,S | Demoted to reserve roster | | | Before |
| 9/18/2012 | CIO | Jimenez,U | Demoted to reserve roster | | | Before |
| 9/19/2012 | CIO | Cordero | Demoted to reserve roster | | | Before |
| 9/19/2012 | CIO | Germano,J | Demoted to reserve roster | | | Before |
| 9/19/2012 | CIO | Jimenez,U | Promoted to active roster | | | Before |
| 9/19/2012 | HAR | De La Rosa,D | Demoted to reserve roster | | | Before |
| 9/19/2012 | HAR | Ottavino | Demoted to reserve roster | | | Before |
| 9/19/2012 | SOI | Betancourt,Y | Demoted to reserve roster | | | Before |
| 9/19/2012 | SOI | Murphy,DT | Promoted to active roster | | | Before |
| 9/20/2012 | BRK | Kelly,D | Demoted to reserve roster | | | Before |
| 9/20/2012 | CIO | Burriss | Promoted to active roster | | | Before |
| 9/20/2012 | CIO | Carreno | Promoted to active roster | | | Before |
| 9/20/2012 | CIO | Raburn | Demoted to reserve roster | | | Before |
| 9/20/2012 | CIO | Rhymes | Promoted to active roster | | | Before |
| 9/20/2012 | CSS | Mathis | Promoted to active roster | | | Before |
| 9/20/2012 | CSS | Ruiz | Demoted to reserve roster | | | Before |
| 9/20/2012 | NYD | Gearrin | Demoted to reserve roster | | | Before |
| 9/21/2012 | ANN | Greinke | Promoted to active roster | | | Before |
| 9/21/2012 | ANN | Nolasco | Promoted to active roster | | | Before |
| 9/21/2012 | CIO | Kennedy.A | Signed | | | Before |
| 9/21/2012 | FDH | Blackley,T | Promoted to active roster | | | Before |
| 9/21/2012 | SOI | Mortensen | Signed | | | Before |
| 9/21/2012 | SOI | Moyer | Demoted to reserve roster | | | Before |
| 9/22/2012 | CIO | Hernandez,Ra | Demoted to reserve roster | | | Before |
| 9/22/2012 | CIO | Mather | Demoted to reserve roster | | | Before |
| 9/22/2012 | CIO | Mather | Promoted to active roster | | | Before |
| 9/22/2012 | FDH | Lohse | Demoted to reserve roster | | | Before |
| 9/23/2012 | ANN | Aoki | Demoted to reserve roster | | | Before |
| 9/23/2012 | ANN | Cedeno,R | Promoted to active roster | | | Before |
| 9/23/2012 | ANN | Gregorius | Promoted to active roster | | | Before |
| 9/23/2012 | ANN | Heisey | Promoted to active roster | | | Before |
| 9/23/2012 | ANN | Ishikawa | Promoted to active roster | | | Before |
| 9/23/2012 | ANN | Napoli | Demoted to reserve roster | | | Before |
| 9/23/2012 | BRK | Straily | Demoted to reserve roster | | | Before |
| 9/23/2012 | CIO | Machado | Demoted to reserve roster | | | Before |
| 9/23/2012 | CIO | Mather | Promoted to active roster | | | Before |
| 9/23/2012 | NYD | Familia | Promoted to active roster | | | Before |
| 9/23/2012 | NYD | Swarzak | Demoted to reserve roster | | | Before |
| 9/25/2012 | BRK | Hill,K | Demoted to reserve roster | | | Before |
| 9/25/2012 | BRK | Vizquel | Demoted to reserve roster | | | Before |
| 9/25/2012 | BRK | Whiteside | Demoted to reserve roster | | | Before |
| 9/25/2012 | CIO | Lillibridge,B | Promoted to active roster | | | Before |
| 9/25/2012 | CIO | Mather | Demoted to reserve roster | | | Before |
| 9/25/2012 | CIO | Wang | Demoted to reserve roster | | | Before |
| 9/25/2012 | CSS | Gonzalez,Mig | Promoted to active roster | | | Before |
| 9/25/2012 | CSS | McCarthy | Demoted to reserve roster | | | Before |
| 9/25/2012 | CSS | Teheran | Promoted to active roster | | | Before |
| 9/25/2012 | FDH | Fontenot | Demoted to reserve roster | | | Before |
| 9/25/2012 | NYD | Blanton | Demoted to reserve roster | | | Before |
| 9/26/2012 | BRK | Hinske | Promoted to active roster | | | Before |
| 9/26/2012 | BRK | Morgan | Promoted to active roster | | | Before |
| 9/26/2012 | BRK | Nady | Promoted to active roster | | | Before |
| 9/26/2012 | CIO | Lillibridge,B | Demoted to reserve roster | | | Before |
| 9/26/2012 | CIO | Valencia,D | Promoted to active roster | | | Before |
| 9/26/2012 | HAR | Simmons | Demoted to reserve roster | | | Before |
| 9/26/2012 | NYD | Bergesen | Promoted to active roster | | | Before |
| 9/26/2012 | NYD | Gregg | Demoted to reserve roster | | | Before |
| 9/27/2012 | CIO | Mather | Promoted to active roster | | | Before |
| 9/27/2012 | CIO | Valencia,D | Demoted to reserve roster | | | Before |
| 9/27/2012 | CSS | Cook,R | Demoted to reserve roster | | | Before |
| 9/27/2012 | CSS | Jeffress | Promoted to active roster | | | Before |
| 9/27/2012 | CSS | Moore,S | Demoted to reserve roster | | | Before |
| 9/27/2012 | CSS | Ross,R | Promoted to active roster | | | Before |
| 9/28/2012 | CIO | Mather | Demoted to reserve roster | | | Before |
| 9/28/2012 | CIO | Sogard | Promoted to active roster | | | Before |
| 9/28/2012 | CSS | Buehrle | Demoted to reserve roster | | | Before |
| 9/28/2012 | FDH | Ramos,W | Promoted to active roster | | | Before |
| 9/28/2012 | HAR | Eaton | Demoted to reserve roster | | | Before |
| 9/28/2012 | HHR | LeMahieu | Demoted to reserve roster | | | Before |
| 9/28/2012 | NYD | Correia | Demoted to reserve roster | | | Before |
| 9/28/2012 | SOI | Chavez.En | Demoted to reserve roster | | | Before |
| 9/28/2012 | SOI | Suzuki,I | Promoted to active roster | | | Before |
| 9/29/2012 | ANN | Greinke | Demoted to reserve roster | | | Before |
| 9/29/2012 | CIO | Escobar,E | Promoted to active roster | | | Before |
| 9/29/2012 | CIO | Lillibridge,B | Promoted to active roster | | | Before |
| 9/29/2012 | CIO | Machado | Promoted to active roster | | | Before |
| 9/29/2012 | CIO | Pena,B | Promoted to active roster | | | Before |
| 9/29/2012 | CIO | Sanchez,J | Promoted to active roster | | | Before |
| 9/29/2012 | CIO | Valencia,D | Promoted to active roster | | | Before |
| 9/29/2012 | CSS | Gonzalez,Mig | Demoted to reserve roster | | | Before |
| 9/29/2012 | FDH | Hamels | Demoted to reserve roster | | | Before |
| 9/29/2012 | NYD | Albers | Promoted to active roster | | | Before |
| 9/29/2012 | NYD | Familia | Demoted to reserve roster | | | Before |
| 9/30/2012 | CIO | Gordon,D | Demoted to reserve roster | | | Before |
| 9/30/2012 | CSS | Bixler | Promoted to active roster | | | Before |
| 9/30/2012 | CSS | Blevins | Promoted to active roster | | | Before |
| 9/30/2012 | CSS | Cain,L | Demoted to reserve roster | | | Before |
| 9/30/2012 | CSS | Flowers | Demoted to reserve roster | | | Before |
| 9/30/2012 | CSS | Hanrahan | Demoted to reserve roster | | | Before |
| 9/30/2012 | CSS | Janish | Promoted to active roster | | | Before |
| 9/30/2012 | CSS | Petersen | Promoted to active roster | | | Before |
| 9/30/2012 | CSS | Putz | Demoted to reserve roster | | | Before |
| 9/30/2012 | CSS | Smith,J | Demoted to reserve roster | | | Before |
| 9/30/2012 | CSS | Wise,D | Promoted to active roster | | | Before |
| 9/30/2012 | FDH | Affeldt | Demoted to reserve roster | | | Before |
| 9/30/2012 | FDH | Anderson,BD | Promoted to active roster | | | Before |
| 9/30/2012 | FDH | Boxberger | Promoted to active roster | | | Before |
| 9/30/2012 | FDH | Burton | Demoted to reserve roster | | | Before |
| 9/30/2012 | FDH | Cain,M | Demoted to reserve roster | | | Before |
| 9/30/2012 | FDH | Cashner | Promoted to active roster | | | Before |
| 9/30/2012 | FDH | De Vries | Promoted to active roster | | | Before |
| 9/30/2012 | FDH | Ellis,AJ | Demoted to reserve roster | | | Before |
| 9/30/2012 | FDH | Kendrick,H | Demoted to reserve roster | | | Before |
| 9/30/2012 | FDH | Lalli | Promoted to active roster | | | Before |
| 9/30/2012 | FDH | McHugh | Promoted to active roster | | | Before |
| 9/30/2012 | FDH | Nathan | Demoted to reserve roster | | | Before |
| 9/30/2012 | FDH | Nathan | Promoted to active roster | | | Before |
| 9/30/2012 | FDH | Ramos,W | Demoted to reserve roster | | | Before |
| 9/30/2012 | FDH | Romo | Demoted to reserve roster | | | Before |
| 9/30/2012 | FDH | Romo | Promoted to active roster | | | Before |
| 9/30/2012 | FDH | Seager | Demoted to reserve roster | | | Before |
| 9/30/2012 | FDH | Strasburg | Demoted to reserve roster | | | Before |
| 9/30/2012 | FDH | Upton,BJ | Demoted to reserve roster | | | Before |
| 9/30/2012 | FDH | Upton,J | Demoted to reserve roster | | | Before |
| 9/30/2012 | FDH | Votto | Demoted to reserve roster | | | Before |
| 9/30/2012 | FDH | Williams | Promoted to active roster | | | Before |