The 36-year-old, a native of Carseland, Alta., has not pitched in the majors since 2001.
"Jeff threw for us last week in Arizona and we were impressed,'' Mariners general manager Jack Zduriencik said. "The ball came out of his hand nice and easy. Our doctors have checked him out and we've determined he's a guy worth taking a chance on.''
Zimmerman had Tommy John elbow surgery in 2002 and retired the next year.
He originally signed with the Texas Rangers after pitching with the Winnipeg Goldeyes in the independent Northern League. He made his Major League Baseball debut in 1999, posting a 9-3 mark with three saves in 65 games.
After pitching in middle relief in 2000, Zimmerman closed for the Rangers in 2001, converting 28 of 31 opportunities. He was placed on the disabled list to begin the 2002 season with an injured right elbow.
Zimmerman has a 17-12 lifetime record with 32 saves and a 3.27 earned-run average.