Mariners Roster & Staff
Transactions
| Date | Transaction |
| 04/30/18 | Seattle Mariners signed free agent C Ortwin Pieternella to a minor league contract. |
| 04/26/18 | Seattle Mariners optioned 1B Daniel Vogelbach to Tacoma Rainiers. |
| 04/26/18 | Seattle Mariners activated 1B Ryon Healy from the 10-day injured list. |
| 04/25/18 | Seattle Mariners sent LHP Dario Alvarez outright to Tacoma Rainiers. |
| 04/23/18 | Seattle Mariners optioned LHP Roenis Elias to Tacoma Rainiers. |
| 04/23/18 | Boston Red Sox traded LHP Roenis Elias to Seattle Mariners for Player To Be Named Later. |
| 04/22/18 | Seattle Mariners activated RHP Erasmo Ramirez from the 10-day disabled list. |
| 04/22/18 | Arizona Diamondbacks traded RHP Edwin Quezada to Seattle Mariners for Future Considerations. |
| 04/22/18 | Seattle Mariners optioned LF Guillermo Heredia to Tacoma Rainiers. |
| 04/20/18 | Seattle Mariners activated C Mike Zunino from the 10-day disabled list. |
| 04/20/18 | Seattle Mariners optioned C Mike Marjama to Tacoma Rainiers. |
| 04/20/18 | Seattle Mariners sent 1B Ryon Healy on a rehab assignment to Arkansas Travelers. |
| 04/18/18 | Ben Gamel roster status changed by Seattle Mariners. |
| 04/18/18 | Seattle Mariners optioned LHP Ariel Miranda to Tacoma Rainiers. |
| 04/17/18 | Seattle Mariners optioned SS Taylor Motter to Tacoma Rainiers. |
| 04/17/18 | Seattle Mariners recalled Ariel Miranda from Tacoma Rainiers. |
| 04/16/18 | Seattle Mariners sent C Mike Zunino on a rehab assignment to Modesto Nuts. |
| 04/14/18 | Seattle Mariners optioned RHP Casey Lawrence to Tacoma Rainiers. |
| 04/14/18 | Seattle Mariners activated DH Nelson Cruz from the 10-day disabled list. |
| 04/10/18 | Seattle Mariners sent RHP Erasmo Ramirez on a rehab assignment to Tacoma Rainiers. |
| 04/10/18 | Seattle Mariners sent OF Ben Gamel on a rehab assignment to Tacoma Rainiers. |
| 04/09/18 | Seattle Mariners signed free agent C Chris Herrmann to a minor league contract. |
| 04/09/18 | Seattle Mariners placed 1B Ryon Healy on the 10-day disabled list retroactive to April 8, 2018. Sprained right ankle. |
| 04/09/18 | Seattle Mariners recalled Chasen Bradford from Tacoma Rainiers. |
| 04/07/18 | Seattle Mariners sent RHP Erasmo Ramirez on a rehab assignment to Modesto Nuts. |
| 04/05/18 | Seattle Mariners sent LF Ben Gamel on a rehab assignment to Modesto Nuts. |
| 04/05/18 | Seattle Mariners signed free agent SS Jery Hernandez to a minor league contract. |
| 04/05/18 | Seattle Mariners signed free agent RHP Josias De Los Santos to a minor league contract. |
| 04/05/18 | Seattle Mariners signed free agent RHP Carlos German to a minor league contract. |
| 04/03/18 | Seattle Mariners signed free agent OF Jayson Werth to a minor league contract. |
| 04/03/18 | Seattle Mariners recalled Taylor Motter from Tacoma Rainiers. |
| 04/03/18 | Seattle Mariners placed DH Nelson Cruz on the 10-day disabled list retroactive to April 1, 2018. Sprained right ankle. |
| 04/02/18 | Seattle Mariners sent CF Cameron Perkins outright to Tacoma Rainiers. |