The veteran relief pitcher was placed on the 15-day DL Saturday retroactive to July 17 with right forearm tightness, the team announced in a release.
Frasor, 34, is the team's all-time leader in career pitching appearances with 497 and has a 1-1 record with a 4.00 earned-run average in 42 games this season with the Jays.
The Oak Forest, Ill. native is in his ninth major league season and has 12 holds and 45 strikeouts in 36 innings.
The move comes a day after Toronto acquired some pitching depth in a 10-player swap with the Houston Astros, nabbing lefty starter J.A. Happ and relievers Brandon Lyon and Dan Carpenter while giving up Ben Francisco, Francisco Cordero and some minor league pitchers.
Toronto's pitching staff has seen its fair share of injuries this season, with Brandon Morrow, Jesse Litsch, Dustin McGowan, Kyle Drabek, Drew Hutchison and reliever Luis Perez for all or parts of the season due to various ailments.
The Jays are still in contention for a wild-card berth, sitting 3.5 games behind the Detroit Tigers for the final playoff spot heading into Saturday's games.