Mariners Roster & Staff
Transactions
| Date | Transaction |
| 05/14/21 | Seattle Mariners recalled 2B Donovan Walton from Tacoma Rainiers. |
| 05/14/21 | Seattle Mariners placed 3B Ty France on the 10-day injured list. Left wrist inflammation. |
| 05/14/21 | Seattle Mariners recalled 2B Jack Mayfield from Tacoma Rainiers. |
| 05/14/21 | Seattle Mariners placed 1B Evan White on the 10-day injured list. Left hip flexor strain. |
| 05/13/21 | Seattle Mariners placed RHP Ljay Newsome on the 60-day injured list. UCL injury. |
| 05/13/21 | Seattle Mariners optioned LHP Aaron Fletcher to Tacoma Rainiers. |
| 05/13/21 | Seattle Mariners selected the contract of RHP Paul Sewald from Tacoma Rainiers. |
| 05/13/21 | Seattle Mariners signed free agent LHP David Huff to a minor league contract. |
| 05/13/21 | Seattle Mariners selected the contract of OF Jarred Kelenic from Tacoma Rainiers. |
| 05/13/21 | Seattle Mariners optioned RHP Wyatt Mills to Tacoma Rainiers. |
| 05/13/21 | Seattle Mariners placed LHP Nick Margevicius on the 60-day injured list. Left shoulder inflammation. |
| 05/13/21 | Seattle Mariners designated CF Braden Bishop for assignment. |
| 05/13/21 | Seattle Mariners optioned LF Taylor Trammell to Tacoma Rainiers. |
| 05/13/21 | Seattle Mariners selected the contract of RHP Logan Gilbert from Tacoma Rainiers. |
| 05/12/21 | Seattle Mariners signed free agent RHP Tyler Herb to a minor league contract. |
| 05/12/21 | Seattle Mariners signed free agent 3B Eric Campbell to a minor league contract. |
| 05/10/21 | Seattle Mariners signed free agent C Caleb Joseph to a minor league contract. |
| 05/09/21 | Seattle Mariners placed RHP Ljay Newsome on the 10-day injured list. Right elbow inflammation. |
| 05/09/21 | Seattle Mariners selected the contract of RHP JT Chargois from Tacoma Rainiers. |
| 05/07/21 | Seattle Mariners signed free agent RHP Brooks Pounders to a minor league contract. |
| 05/07/21 | Seattle Mariners signed free agent RHP Justin Grimm to a minor league contract. |
| 05/05/21 | LHP Hector Santiago assigned to Seattle Mariners. |
| 05/05/21 | Seattle Mariners placed RHP Keynan Middleton on the 10-day injured list. Right biceps strain. |
| 05/05/21 | Seattle Mariners recalled RHP Wyatt Mills from Tacoma Rainiers. |
| 05/04/21 | Seattle Mariners activated 1B Evan White from the 10-day injured list. |
| 05/04/21 | Seattle Mariners signed free agent RHP Ryan Dull to a minor league contract. |
| 05/04/21 | Seattle Mariners recalled LHP Aaron Fletcher from Tacoma Rainiers. |
| 05/04/21 | Seattle Mariners optioned RHP Domingo Tapia to Tacoma Rainiers. |
| 05/04/21 | Seattle Mariners optioned RHP Wyatt Mills to Tacoma Rainiers. |
| 05/03/21 | Boston Red Sox claimed RHP Brandon Brennan off waivers from Seattle Mariners. |
| 05/03/21 | Seattle Mariners placed 1B Evan White on the 10-day injured list. |
| 05/03/21 | Seattle Mariners signed free agent RHP Matt Pierpont to a minor league contract. |
| 05/02/21 | Seattle Mariners traded C Jacob Nottingham to Milwaukee Brewers for cash. |
| 05/02/21 | Seattle Mariners placed RHP Casey Sadler on the 10-day injured list. Right shoulder inflammation. |
| 05/02/21 | Seattle Mariners recalled RHP Erik Swanson from Tacoma Rainiers. |
| 05/01/21 | Seattle Mariners designated C Jacob Nottingham for assignment. |
| 05/01/21 | Seattle Mariners recalled RHP Wyatt Mills from Tacoma Rainiers. |
