The Mariners selected Vosler's contract from Triple-A Tacoma on Monday.
The 30-year-old has slashed .289/.357/.526 with 20 home runs over 89 games this season with Tacoma, mostly playing first base and right field but also seeing action at third base and in left field. Previous reports suggested that the Mariners would recall Tyler Locklear from Triple-A Tacoma after first baseman Ty France was placed on outright waivers, so Vosler could just be a roster stopgap until France's situation is resolved.