| | | Friday, October 12th, 2012 | | Placed SP Arturo Ruíz on the active roster. | | Activated SP Arturo Ruíz from the 60-day disabled list. |
| Monday, August 20th, 2012 | | 3B Juan Alonzo was designated for assignment and placed on waivers. |
| Monday, August 6th, 2012 | | Placed CF Eric Keller on the 14-day disabled list, retroactive to 08/02/2012. | | Purchased the contract of CF Matt Smith from Triple A Mdewanketon. |
| Sunday, July 8th, 2012 | | Signed SP Guillermo Martínez to a 3-year contract extension worth a total of $33,500,000. |
| Tuesday, June 26th, 2012 | | Placed SP Arturo Ruíz on the 60-day disabled list. |
| Monday, June 25th, 2012 | | Signed 2B Marvin Welch to a 5-year contract extension worth a total of $78,200,000. |
| Friday, June 15th, 2012 | | Signed LF Joe Booth to a 4-year contract extension worth a total of $25,200,000. |
| Tuesday, June 5th, 2012 | | Signed MR Pedro Morales to a 3-year contract extension worth a total of $3,900,000. |
| Saturday, June 2nd, 2012 | | Signed CF Eric Keller to a 2-year contract extension worth a total of $2,600,000. |
| Friday, June 1st, 2012 | | Signed MR Arnold Hall to a 2-year contract extension worth a total of $2,800,000. |
| Monday, April 30th, 2012 | | Placed SS Chip Render on the 14-day disabled list, retroactive to 04/25/2012. | | Purchased the contract of RF Zach Milford from Triple A Mdewanketon. |
| Friday, January 13th, 2012 | | Signed hitting coach Tim Johnson to a 5-year, $370,000 per year contract. |
| Wednesday, January 4th, 2012 | | Signed manager José Hernández to a 5-year, $750,000 per year contract. |
| Tuesday, January 3rd, 2012 | | Signed bench coach Javier Ramírez to a 3-year, $650,000 per year contract. | | Signed team doctor Bill Nauss to a 5-year, $650,000 per year contract. |
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