Key additions and subtractions for the Mariners since the end of the 2010 season.
| Date | Added | Skinny | |
|---|---|---|---|
| Dec. 10 | DH Jack Cust | Signed as a free agent | |
| Dec. 11 | C Miguel Olivo | Free agent signed a two-year, $7 million deal | |
| Dec. 12 | INF Brendan Ryan | Acquired in a trade from St. Louis | |
| Date | Subtracted | Skinny | |
| Nov. 3 | OF Ryan Langerhans | Outrighted to Tacoma, elected free agency | |
| Nov. 4 | 1B Casey Kotchman | Non-tendered, became a free agent | |
| Nov. 7 | RHP Jamey Wright | Non-tendered, became a free agent | |
| DH Russell Branyan | Non-tendered, became a free agent | ||
| Ç Josh Bard | Elected to become a free agent | ||
| Dec. 2 | LHP Ryan Rowland-Smith | Non-tendered, became a free agent | |
| 3B Jose Lopez | Traded to the Colorado Rockies for Chaz Roe | ||
| Dec. 13 | C Rob Johnson | Designated for assignment |