The Seattle Mariners 2003 season was their 27th since the franchise creation, and ended the season finishing 2nd in the American League West, finishing with a record of 93-69.
- October 11, 2002: Scott Podsednik was selected off waivers by the Milwaukee Brewers from the Seattle Mariners.
- December 6, 2002: John Olerud was signed as a Free Agent with the Seattle Mariners.
- January 16, 2003: John Mabry was signed as a Free Agent with the Seattle Mariners.
Opening Day starters
- Bret Boone
- Mike Cameron
- Jeff Cirillo
- Carlos Guillén
- Mark McLemore
- Jamie Moyer
- John Olerud
- Ichiro Suzuki
- Dan Wilson
- Randy Winn 
- July 29, 2003: Kenny Kely was traded by the Seattle Mariners to the New York Mets for Rey Sanchez and cash.
Starters by position
Note: Pos = Position; G = Games played; AB = At Bats; H = Hits; Avg. = Batting Average; HR = Home Runs; RBI = Runs Batted In
Note: G = Games played; AB = At Bats; H = Hits; Avg. = Batting Average; HR = Home Runs; RBI = Runs Batted In
Awards and honors
2003 Major League Baseball All-Star Game
LEAGUE CHAMPIONS: San Antonio, Inland Empire