| | P | Sent to Minors (The Seattle Mariners sent RHP Ty Buttrey to the minors.) |
| | CF | Sent to Minors (The Seattle Mariners optioned OF Jonatan Clase to the minors.) |
| | SS | Released (The Seattle Mariners released INF Cole Tucker.) |
| | | Traded (The Seattle Mariners traded RHP Natanael Garabitos to the Kansas City Royals.) To |
| | P | Sent to Minors (The Seattle Mariners sent RHP Mauricio Llovera outright to the minors.) |
| | SS | Sent to Minors (The Seattle Mariners assigned INF Cole Young to minor league camp.) |
| | SS | Sent to Minors (The Seattle Mariners assigned INF Cole Tucker to minor league camp.) |
| | 3B | Sent to Minors (The Seattle Mariners assigned INF Tyler Locklear to minor league camp.) |
| | C | Sent to Minors (The Seattle Mariners assigned C Harry Ford to minor league camp.) |
| | P | Sent to Minors (The Seattle Mariners assigned LHP Kirby Snead to minor league camp.) |
| | P | Sent to Minors (The Seattle Mariners sent RHP Marcelo Perez to the minors.) |
| | P | Sent to Minors (The Seattle Mariners optioned RHP Levi Stoudt to the minors.) |
| | P | Sent to Minors (The Seattle Mariners sent RHP Trevor Kelley to the minors.) |
| | P | Sent to Minors (The Seattle Mariners optioned RHP Ty Adcock to the minors.) |
| | 1B | Signed (The Seattle Mariners signed INF Jason Vosler to a minor league contract.) |
| | CF | Sent to Minors (The Seattle Mariners sent OF Isiah Gilliam to the minors.) |
| | C | Sent to Minors (The Seattle Mariners optioned C Blake Hunt to the minors.) |
| | P | Sent to Minors (The Seattle Mariners sent LHP Reid VanScoter to the minors.) |
| | CF | Signed (The Seattle Mariners signed OF Grant Witherspoon to a minor league contract.) |
| | LF | Sent to Minors (The Seattle Mariners sent OF Nick Solak to the minors.) |
| | 1B | Sent to Minors (The Seattle Mariners sent INF Michael Chavis to the minors.) |
| | P | Signed (The Seattle Mariners signed RHP Ryne Stanek.) |
| | P | Activated (The Seattle Mariners signed RHP Ryne Stanek.) |
| | P | Sent to Minors (The Seattle Mariners assigned RHP Cory Abbott to minor league camp.) |
| | P | Sent to Minors (The Seattle Mariners assigned LHP Holden Laws to minor league camp.) |
| | P | Sent to Minors (The Seattle Mariners assigned RHP Sean Poppen to minor league camp.) |
| | P | Sent to Minors (The Seattle Mariners assigned RHP Heath Hembree to minor league camp.) |
| | 1B | Sent to Minors (The Seattle Mariners assigned INF Rangel Ravelo to minor league camp.) |
| | P | Sent to Minors (The Seattle Mariners assigned RHP Jimmy Joyce to minor league camp.) |
| | P | Sent to Minors (The Seattle Mariners assigned RHP Travis Kuhn to minor league camp.) |
| | 3B | Signed (The Seattle Mariners signed INF Brian Anderson to a minor league contract.) |
| | 3B | Non-roster Invitee (The Seattle Mariners invited INF Brian Anderson to spring training.) |
| | 3B | Signed (The Seattle Mariners signed INF Brian Anderson to a minor league contract.) |
| | RF | Designated for Assignment (The Seattle Mariners designated OF Canaan Smith-Njigba for assignment.) |
| | P | Claimed on Unconditional Release Waivers (The Seattle Mariners claimed RHP Levi Stoudt off waivers from the Cincinnati Reds.) |
| | P | Signed (The Seattle Mariners signed RHP Jordan Holloway to a minor league contract.) |
| | P | Traded (The Seattle Mariners traded RHP Darren McCaughan to the Miami Marlins.) To |
| | P | Signed (The Seattle Mariners signed RHP Braden Shipley to a minor league contract.) |
| | P | Signed (The Seattle Mariners signed RHP Braden Shipley to a minor league contract.) |
| | P | Non-roster Invitee (The Seattle Mariners signed RHP Casey Lawrence with an invitation to spring training.) |
| | P | Signed (The Seattle Mariners signed RHP Sean Poppen to a minor league contract with an invitation to spring training.) |
| | RF | Claimed on Unconditional Release Waivers (The Seattle Mariners claimed OF Canaan Smith-Njigba.) |
| | P | Designated for Assignment (The Seattle Mariners designated RHP Darren McCaughan for assignment.) |
| | CF | Non-roster Invitee (The Seattle Mariners signed OF Isiah Gilliam to a minor league contract with an invitation to spring training.) |
| | P | Claimed on Unconditional Release Waivers (The Seattle Mariners claimed RHP Collin Snider off waivers from the Arizona Diamondbacks.) |
| | P | Traded (The Seattle Mariners traded RHP Prelander Berroa to the Chicago White Sox.) To |
| | CF | Traded (The Seattle Mariners traded OF Zach DeLoach to the Chicago White Sox.) To |
| | P | Traded (The Chicago White Sox traded RHP Gregory Santos to the Seattle Mariners.) From |
| | P | Signed (The Seattle Mariners signed RHP Heath Hembree to a minor league contract.) |
| | P | Traded (The Seattle Mariners traded RHP Anthony DeSclafani to the Minnesota Twins.) To |
| | P | Traded (The Seattle Mariners traded RHP Justin Topa to the Minnesota Twins.) To |
| | CF | Traded (The Seattle Mariners traded OF Gabriel Gonzalez to the Minnesota Twins.) To |
| | 2B | Signed (The Minnesota Twins traded INF Jorge Polanco to the Seattle Mariners.) |
| | 2B | Traded (The Kansas City Royals traded INF Samad Taylor to the Seattle Mariners.) From |
| | LF | Non-roster Invitee (The Seattle Mariners signed OF Nick Solak to a minor league contract with an invitation to spring training.) |
| | P | Traded (The Seattle Mariners traded RHP Justin Topa to the Minnesota Twins.) To |
| | CF | Traded (The Seattle Mariners traded OF Gabriel Gonzalez to the Minnesota Twins.) To |
| | 2B | Signed (The Minnesota Twins traded INF Jorge Polanco to the Seattle Mariners.) |
| | P | Traded (The Seattle Mariners traded RHP Darren Bowen to the Minnesota Twins.) To |
| | 2B | Traded (The Minnesota Twins traded INF Jorge Polanco to the Seattle Mariners.) From |
| | P | Traded (The Seattle Mariners traded RHP Anthony DeSclafani to the Minnesota Twins.) To |
| | 1B | Signed (The Seattle Mariners signed INF Michael Papierski to a minor league contract.) |
| | P | Signed (The Seattle Mariners signed RHP Austin Voth.) |
| | P | Signed (The Seattle Mariners signed RHP Ty Buttrey to a minor league contract.) |
| | P | Signed (The Seattle Mariners signed RHP Ty Buttrey to a minor league contract.) |
| | 1B | Signed (The Seattle Mariners signed INF Michael Chavis to a minor league contract with an invitation to spring training.) |
| | P | Claimed on Unconditional Release Waivers (The Seattle Mariners claimed RHP Mauricio Llovera off waivers.) |
| | P | Traded (The San Francisco Giants traded RHP Anthony DeSclafani to the Seattle Mariners.) From |
| | P | Traded (The Seattle Mariners traded LHP Robbie Ray to the San Francisco Giants.) To |
| | 1B | Traded (The Tampa Bay Rays traded OF Luke Raley to the Seattle Mariners.) From |
| | SS | Traded (The Seattle Mariners traded INF José Caballero to the Tampa Bay Rays.) To |
| | LF | Traded (The San Francisco Giants traded OF Mitch Haniger to the Seattle Mariners.) From |
| | P | Signed (The Seattle Mariners signed RHP Brett de Geus to a minor league contract.) |
| | P | Traded (The Atlanta Braves traded RHP Jackson Kowar to the Seattle Mariners.) From |
| | P | Traded (The Seattle Mariners traded LHP Marco Gonzales to the Atlanta Braves.) To |
| | LF | Traded (The Seattle Mariners traded OF Jarred Kelenic to the Atlanta Braves.) To |
| | 1B | Traded (The Seattle Mariners traded INF Evan White to the Atlanta Braves.) To |
| | P | Traded (The Atlanta Braves traded RHP Cole Phillips to the Seattle Mariners.) From |
| | C | Waived (The Seattle Mariners waived DH Cooper Hummel.) |
| | P | Designated for Assignment (The Seattle Mariners designated RHP Kaleb Ort for assignment.) |
| | P | Designated for Assignment (The Seattle Mariners designated RHP Ryan Jensen for assignment.) |
| | C | Traded (The Arizona Diamondbacks traded C Seby Zavala to the Seattle Mariners.) From |
| | P | Traded (The Arizona Diamondbacks traded RHP Carlos Vargas to the Seattle Mariners.) From |
| | 3B | Traded (The Seattle Mariners traded INF Eugenio Suárez to the Arizona Diamondbacks.) To |
| | 1B | Released (The Seattle Mariners released INF Mike Ford.) |
| | P | Traded (The Seattle Mariners traded RHP Isaiah Campbell to the Boston Red Sox.) To |
| | 3B | Traded (The Boston Red Sox traded INF Luis Urías to the Seattle Mariners.) From |
| | 1B | Designated for Assignment (The Seattle Mariners designated INF Mike Ford for assignment.) |
| | CF | Recalled From Minors Rehab (The Seattle Mariners selected the contract of OF Zach DeLoach from the minors.) |
| | P | Signed (The Seattle Mariners signed RHP Tyson Miller to a minor league contract.) |
| | RF | Declared Free Agency (INF Robert Perez declared free agency.) |
| | P | Declared Free Agency (RHP Marcus Walden declared free agency.) |
| | C | Declared Free Agency (C Josh Morgan declared free agency.) |
| | C | Declared Free Agency (C Brian O'Keefe declared free agency.) |
| | P | Declared Free Agency (RHP Joseph Yabbour declared free agency.) |
| | P | Declared Free Agency (RHP A.J. Puckett declared free agency.) |
| | P | Declared Free Agency (RHP Dayeison Arias declared free agency.) |
| | LF | Declared Free Agency (OF Ty Kelly declared free agency.) |
| | P | Declared Free Agency (RHP Juan Then declared free agency.) |
| | P | Declared Free Agency (RHP Kelvin Nunez declared free agency.) |
| | LF | Declared Free Agency (OF Walking Cabrera declared free agency.) |
| | C | Declared Free Agency (C Robert Emery declared free agency.) |
| | 1B | Declared Free Agency (INF Robbie Tenerowicz declared free agency.) |
| | P | Declared Free Agency (RHP Collin Kober declared free agency.) |
| | P | Declared Free Agency (RHP Adam Oller declared free agency.) |
| | SS | Declared Free Agency (INF Logan Warmoth declared free agency.) |
| | P | Declared Free Agency (RHP Sam Carlson declared free agency.) |
| | P | Declared Free Agency (RHP Ryder Ryan declared free agency.) |
| | CF | Declared Free Agency (OF Adam Engel declared free agency.) |
| | P | Declared Free Agency (RHP Taylor Williams declared free agency.) |
| | 3B | Declared Free Agency (INF Jake Scheiner declared free agency.) |
| | 3B | Declared Free Agency (INF Connor Hoover declared free agency.) |
| | P | Declared Free Agency (RHP Kyle Tyler declared free agency.) |
| | P | Declared Free Agency (RHP Michael Flynn declared free agency.) |
| | P | Declared Free Agency (RHP Nick Wittgren declared free agency.) |
| | P | Declared Free Agency (RHP Casey Sadler declared free agency.) |
| | P | Declared Free Agency (LHP Rob Kaminsky declared free agency.) |
| | P | Declared Free Agency (LHP Kyle Hart declared free agency.) |
| | C | Declared Free Agency (C Pedro Severino declared free agency.) |
| | P | Declared Free Agency (RHP Easton McGee declared free agency.) |
| | P | Declared Free Agency (RHP Shawn Semple declared free agency.) |
| | P | Declared Free Agency (LHP Zach Muckenhirn declared free agency.) |
| | P | Declared Free Agency (LHP Logan Allen declared free agency.) |
| | P | Declared Free Agency (LHP Jorge Benitez declared free agency.) |
| | P | Declared Free Agency (LHP Blake Weiman declared free agency.) |
| | P | Declared Free Agency (RHP Alex Valverde declared free agency.) |
| | P | Sent to Minors (The Seattle Mariners sent RHP Ryder Ryan outright to the minors.) |
| | P | Traded (The Seattle Mariners traded RHP Riley O'Brien to the St. Louis Cardinals.) To |
| | C | Traded (The Tampa Bay Rays traded C Blake Hunt to the Seattle Mariners.) From |
| | 1B | Activated (The Seattle Mariners activated INF Evan White.) |
| | P | Activated (The Seattle Mariners activated RHP Emerson Hancock.) |
| | P | Activated (The Seattle Mariners activated LHP Robbie Ray.) |
| | P | Designated for Assignment (The Seattle Mariners designated RHP Ryder Ryan for assignment.) |
| | C | Declared Free Agency (C Luis Torrens elected free agency.) |
| | P | Activated (The Seattle Mariners activated LHP Marco Gonzales.) |
| | P | Activated (The Seattle Mariners activated RHP Ryder Ryan.) |
| | P | Activated (The Seattle Mariners activated RHP Eduard Bazardo.) |
| | C | Activated (The Seattle Mariners activated DH Cooper Hummel.) |
| | LF | Activated (The Seattle Mariners activated OF Taylor Trammell.) |
| | P | Activated (The Seattle Mariners activated RHP Ryan Jensen.) |
| | CF | Activated (The Seattle Mariners activated OF Jonatan Clase.) |
| | P | Activated (The Seattle Mariners activated RHP Darren McCaughan.) |
| | LF | Activated (The Seattle Mariners activated OF Cade Marlowe.) |
| | P | Activated (The Seattle Mariners activated RHP Ty Adcock.) |
| | RF | Declared Free Agency (Seattle Mariners OF Teoscar Hernández declared free agency.) |
| | P | Traded (The Pittsburgh Pirates traded RHP Cody Bolton to the Seattle Mariners.) From |
| | C | Declared Free Agency (Seattle Mariners C Tom Murphy declared free agency.) |
| | P | Declared Free Agency (Seattle Mariners RHP Dominic Leone declared free agency.) |
| | P | Designated for Assignment (The Seattle Mariners designated RHP Penn Murfee for assignment.) |
| | P | Activated (The Seattle Mariners activated RHP Easton McGee from the 60-day injured list.) |
| | P | Sent to Minors (The Seattle Mariners sent RHP Easton McGee outright to the minors.) |
| | P | Sent to Minors (The Seattle Mariners sent RHP Adam Oller outright to the minors.) |
| | C | Sent to Minors (The Seattle Mariners sent C Luis Torrens outright to the minors.) |
| | P | Activated (The Seattle Mariners activated RHP Penn Murfee from the 60-day injured list.) |
| | C | Sent to Minors (The Seattle Mariners sent C Brian O'Keefe outright to the minors.) |
| | P | Claimed on Unconditional Release Waivers (The Seattle Mariners claimed RHP Kaleb Ort off waivers from the Boston Red Sox.) |
| | C | Designated for Assignment (The Seattle Mariners designated C Brian O'Keefe for assignment.) |
| | P | Declared Free Agency (RHP José Rodríguez declared free agency.) |
| | P | Declared Free Agency (RHP Diego Castillo declared free agency.) |
| | P | Released (The Seattle Mariners released LHP Tommy Milone.) |
| | P | Sent to Minors (The Seattle Mariners optioned RHP Eduard Bazardo to the minors.) |
| | P | Recalled From Minors Rehab (The Seattle Mariners recalled RHP Prelander Berroa from the minors.) |
| | C | Sent to Minors (The Seattle Mariners optioned C Brian O'Keefe to the minors.) |
| | C | Activated (The Seattle Mariners activated C Brian O'Keefe off Paternity Leave.) |
| | C | Recalled From Minors Rehab (The Seattle Mariners selected the contract of C Luis Torrens.) |
| | C | Placed on Paternity Leave List (The Seattle Mariners placed C Brian O'Keefe on the Paternity Leave list.) |
| | LF | Activated (The Seattle Mariners activated OF Jarred Kelenic from the 10-day injured list.) |
| | LF | Sent to Minors (The Seattle Mariners optioned OF Cade Marlowe to the minors.) |
| | P | Designated for Assignment (The Seattle Mariners designated RHP Luke Weaver for assignment.) |
| | P | Recalled From Minors Rehab (The Seattle Mariners recalled RHP Eduard Bazardo from the minors.) |
| | P | Waived (The Seattle Mariners waived RHP Devin Sweet.) |
| | 2B | Recalled From Minors Rehab (The Seattle Mariners recalled INF Sam Haggerty from the minors.) |
| | P | Recalled From Minors Rehab (The Seattle Mariners recalled RHP Dominic Leone from the minors.) |
| | P | Claimed on Unconditional Release Waivers (The Seattle Mariners claimed RHP Dominic Leone off waivers from the Los Angeles Angels.) |
| | P | Designated for Assignment (The Seattle Mariners designated RHP Devin Sweet for assignment.) |
| | P | Recalled From Minors Rehab (The Seattle Mariners recalled RHP Adam Oller from the minors.) |
| | C | Signed (The Seattle Mariners signed C Luis Torrens to a minor league contract.) |
| | C | Signed (The Seattle Mariners signed C Luis Torrens to a minor league contract.) |
| | CF | Released (The Seattle Mariners released OF Tanner Kirwer.) |
| | P | Sent to Minors (The Seattle Mariners optioned RHP Eduard Bazardo to the minors.) |
| | P | Sent to Minors (The Seattle Mariners optioned RHP Darren McCaughan to the minors.) |
| | P | Activated (The Seattle Mariners activated RHP Bryan Woo from the 15-day injured list.) |
| | P | Signed (The Seattle Mariners signed RHP Luke Weaver.) |
| | P | Activated (The Seattle Mariners activated RHP Luke Weaver.) |
| | P | Placed on 60-Day IL (The Seattle Mariners transferred RHP Emerson Hancock to the 60-day injured list. ) |
| | SS | Activated (The Seattle Mariners activated INF J.P. Crawford from the 7-day injured list.) |
| | 2B | Sent to Minors (The Seattle Mariners optioned INF Sam Haggerty to the minors.) |
| | P | Placed on 15-Day IL (The Seattle Mariners placed RHP Emerson Hancock on the 15-day injured list with a right shoulder strain. ) |
| | P | Recalled From Minors Rehab (The Seattle Mariners recalled RHP Darren McCaughan from the minors.) |
| | P | Released (The Seattle Mariners released RHP Nolan Blackwood.) |
| | P | Signed (The Seattle Mariners signed RHP Nick Wittgren to a minor league contract.) |