Shafer was recalled from Triple-A Buffalo on Thursday, Mike Wilner of Sportsnet 590 The Fan reports.
Shafer has made 26 appearances for the Blue Jays this season, posting a 3.19 ERA, 1.68 WHIP and 29:22 K:BB across 31 innings. The right-hander figures to fill a middle-relief role for the rest of the season.