McGowan hasn't pitched in a major league game since he went 6-7 with a 4.37 ERA in 19 starts for the Blue Jays in 2008. He had surgery in June to repair a torn rotator cuff and improve range of motion in his pitching shoulder.
The team announced the deal Thursday and said the 28-year-old McGowan recently started a throwing program. There is no timetable for his return to the mound.
McGowan is 20-22 with a 4.71 ERA in 75 games over four seasons with Toronto.