The 28-year-old Wells is expected to report prior to Toronto's series opener in Kansas City on Friday. By that time, the Blue Jays will have to make a corresponding move to create room on their 25-man roster.
Wells is an above-average defender who hit .225 with 17 home runs and 51 RBIs in 124 games for the Mariners over the past two seasons. He batted .189 with two homers, 14 RBIs and a .646 OPS in 53 at-bats this spring.
The biggest benefit for the Blue Jays is Wells' ability to hit left-handed pitching. Wells is a career .264 hitter with an .838 OPS versus lefties compared to a .230 average and .675 OPS against righties.
The claim likely means Toronto will soon go with a seven-man bullpen. The club had been carrying eight relievers through the first week of the season, but that will soon change, and it's probable that right-hander Edgar Gonzalez will be the one who is designated for assignment.
To make room on the 40-man roster for Wells, the Blue Jays designated right-hander Alex Burnett for assignment.
Gregor Chisholm is a reporter for MLB.com. Read his blog, North of the Border, and follow him on Twitter @gregorMLB. This story was not subject to the approval of Major League Baseball or its clubs.