January 08, 2021

Mariners  sign Roenis Elias

Mariners  sign Paul Sewald

January 14, 2021

Mariners  sign Dillon Thomas

February 09, 2021

Mariners  sign J.T. Chargois as a free agent

February 18, 2021

Mariners  place Andres Munoz on the injured list

Mariners  sign James Paxton as a free agent

February 19, 2021

Mariners  designate Robert Dugger for assignment

Mariners  sign Ken Giles as a free agent

March 25, 2021

Mariners  release Roenis Elias

March 31, 2021

Mariners  place Kyle Lewis on the injured list

Mariners  place Shed Long on the injured list

Mariners  place Ken Giles on the injured list

April 01, 2021

Mariners  sign Roenis Elias as a free agent

April 07, 2021

Mariners  place James Paxton on the injured list

Mariners  place Jake Fraley on the injured list

April 12, 2021

Mariners  place Anthony Misiewicz on the injured list

April 16, 2021

Mariners  place James Paxton on the injured list

April 26, 2021

Mariners  place Nick Margevicius on the injured list

April 27, 2021

Mariners  place Shed Long on the injured list

April 28, 2021

Mariners  designate Brandon Brennan for assignment

April 29, 2021

Mariners  place Marco Gonzales on the injured list

May 01, 2021

Mariners  designate Jacob Nottingham for assignment

May 02, 2021

Mariners  place Casey Sadler on the injured list

Jacob Nottingham traded from Mariners  to Brewers 

May 03, 2021

Mariners  place Evan White on the injured list

May 05, 2021

Mariners  place Keynan Middleton on the injured list

May 07, 2021

Mariners  sign Justin Grimm

May 09, 2021

Mariners  place Ljay Newsome on the injured list

May 12, 2021

Mariners  sign Eric Campbell

May 13, 2021

Mariners  place Nick Margevicius on the injured list

Mariners  place Ljay Newsome on the injured list

Mariners  designate Braden Bishop for assignment

May 14, 2021

Mariners  place Evan White on the injured list

Mariners  place Ty France on the injured list

May 17, 2021

Mariners  designate Domingo Tapia for assignment

May 19, 2021

Mariners  place Dylan Moore on the injured list

May 20, 2021

Mariners  designate Jose Marmolejos for assignment

Mariners  designate Brady Lail for assignment

May 21, 2021

Mariners  place Drew Steckenrider on the injured list

Mariners  place Anthony Misiewicz on the injured list

Mariners  place Will Vest on the injured list

Mariners  place Robert Dugger on the injured list

May 22, 2021

Domingo Tapia traded from Mariners  to Royals 

Mariners  sign Zack Weiss

May 23, 2021

Mariners  place Kendall Graveman on the injured list

May 24, 2021

Mariners  place Sam Haggerty on the injured list

May 29, 2021

Mariners  place Casey Sadler on the injured list

Mariners  place Erik Swanson on the injured list

June 01, 2021

Mariners  place Kyle Lewis on the injured list

June 02, 2021

Mariners  place Justin Dunn on the injured list

June 04, 2021

Yacksel Rios traded from Rays  to Mariners 

June 07, 2021

Mariners  place Sam Haggerty on the injured list

June 08, 2021

Mariners  designate Jacob Nottingham for assignment

June 10, 2021

Mariners  designate Jack Mayfield for assignment

Jake Bauers traded from Indians  to Mariners 

June 11, 2021

Mariners  designate Yacksel Rios for assignment

June 14, 2021

Yacksel Rios traded from Mariners  to Red Sox 

June 18, 2021

Mariners  place Kyle Lewis on the injured list

Mariners  place Justin Dunn on the injured list

June 22, 2021

Mariners  place Evan White on the injured list

June 24, 2021

Mariners  designate Daniel Zamora for assignment

Wyatt Mathisen traded from Rays  to Mariners 

June 28, 2021

Mariners  sign Nate Fisher

July 07, 2021

Mariners  place Justus Sheffield on the injured list

July 11, 2021

Mariners  place Yusei Kikuchi on the injured list

July 12, 2021

Mariners  designate Will Vest for assignment

July 16, 2021

Mariners  designate Wyatt Mathisen for assignment

July 18, 2021

Mariners  place Jake Fraley on the injured list

July 23, 2021

Mariners  designate Rafael Montero for assignment

July 27, 2021

Mariners  designate Vinny Nittoli for assignment

July 28, 2021

Mariners  designate Jake Hager for assignment

Tyler Anderson traded from Pirates  to Mariners 

July 29, 2021

Mariners  sign Asher Wojciechowski

August 02, 2021

Mariners  place Shed Long on the injured list

Mariners  designate Dillon Thomas for assignment

August 19, 2021

Mariners  place Justin Dunn on the injured list

August 21, 2021

Mariners  place Diego Castillo on the injured list

August 22, 2021

Mariners  designate Robert Dugger for assignment

Mariners  sign Matt Andriese as a free agent

August 26, 2021

Mariners  designate Keynan Middleton for assignment

August 28, 2021

Mariners  place Shed Long on the injured list

Mariners  place Anthony Misiewicz on the injured list

Mariners  place Jake Fraley on the injured list

August 30, 2021

Mariners  designate Jimmy Yacabonis for assignment

September 14, 2021

Mariners  designate Jose Marmolejos for assignment

September 28, 2021

Mariners  designate Matt Andriese for assignment

October 02, 2021

Mariners  place Joe Smith on the injured list

October 05, 2021

Jose Marmolejos became a free agent

November 03, 2021

Sean Doolittle became a free agent

Joe Smith became a free agent

Hector Santiago became a free agent

Tyler Anderson became a free agent

James Paxton became a free agent

November 04, 2021

Kyle Seager became a free agent

November 27, 2021

November 30, 2021

Mariners  sign Robbie Ray as a free agent

December 03, 2021

Mariners  sign Brian O'Keefe