Walker can make up to $3 million total based on incentives.
He appeared to confirm the move with a tweet Wednesday:
Let's gooo!! 💪🏾💪🏾 pic.twitter.com/SijPsjyvdt— Taijuan Walker (@tai_walker) February 12, 2020
The move marks a return to Seattle for Walker, who pitched for the Mariners from 2013 to 2016. He spent the past three seasons with the Arizona Diamondbacks.
Walker, 27, missed most of the past two years after Tommy John surgery. He pitched one inning during the final week of the 2019 season. Walker became a free agent after he wasn't tendered a contract by the Diamondbacks.
He is 31-31 with a 3.95 ERA in 94 starts over his career and 97 appearances overall.
The Associated Press contributed to this report.