Ackley signed a minor-league contract with the Mariners on Wednesday, Jon Heyman of FancredSports.com reports.
Ackley is back with the team who drafted him after spending the previous two seasons with the Angels' Triple-A affiliate. The 30-year-old hasn't appeared in the majors since 2016, when he struggled to a .148/.243/.148 slash line across 28 games with the Yankees.