Seattle announced the move on Thursday.
Kotchman was acquired in a trade with the Boston Red Sox last January but hit .217 with 20 doubles, nine homers and 51 RBIs in 125 games for Seattle. It was the lowest batting average of his career and his on-base percentage was just .280.
Also Thursday, new Mariners manager Eric Wedge filled out his coaching staff by hiring former New York Yankees hitting coach Chris Chambliss and longtime San Francisco Giants infielder Robby Thompson.
Thompson will be the Mariners' bench coach and responsible for infield instruction. Chambliss will be Seattle's hitting coach.
Two coaches will return from Seattle's previous staff. Carl Willis, who was Seattle's pitching coach the final two months of last season, will continue in that role under Wedge. Mike Brumley will coach first base and be the Mariners' outfield/baserunning instructor.
Rounding out Seattle's staff are Jeff Datz (third base), Jamie Navarro (bullpen) and Jason Phillips (bullpen catcher).
Information from The Associated Press was used in this report.