The Orioles grabbed a 2-0 lead in the first inning on Adam Jones' two-run homer, but new starter Tommy Hunter gave up two runs in the second and two more in the third.
The Blue Jays never trailed from that point, winning the first game of this series, 5-4, before 18,770 on Fireworks Night at Camden Yards.
Robert Andino singled off Jon Rauch with two outs in the ninth and scored on Nick Markakis' double to right, but Jones popped up an 0-1 pitch to end the game.
Troy Patton was charged with a run in the eighth after loading the bases with no outs. Aaron Hill lifted a sacrifice fly off Chris Jakubauskas, but J.P. Arencibia grounded into a force at the plate and Nolan Reimold threw out Colby Rasmus trying to score on Brett Lawrie's single.
That was Reimold's first outfield assist and the 22nd for the Orioles - including seven at the plate.
Patton retired the first nine batters that he faced.
Jakubauskas threw two scoreless innings. The Orioles' bullpen allowed one run and three hits, with one walk, in five innings.
The Orioles are 13-35 since taking a 30-31 record into a June 11 game against Tampa Bay.
At Triple-A Norfolk, Brandon Snyder's two-run double was his first extra-base hit since July 3.
Former Twin Brendan Harris homered off Kevin Slowey, who would rather be pitching for the Twins than their Triple-A affiliate in Rochester.
In case you forgot about Luis Lebron or wondered if he was pitching in Japan, he tossed a scoreless inning tonight for short-season Single-A Aberdeen.
Updates: Chris Davis was scratched from the lineup with a sore right shoulder, and he'll undergo an MRI tomorrow at 1:45 p.m. Davis was still feeling some discomfort in the shoulder while throwing during batting practice.
J.J. Hardy will have a CT scan on his left ankle.
Zach Britton went on the disabled list as a precaution, and the Orioles think he'll be ready to pitch once the 15 days are up. In fact, he could get a few innings in the minors before he's eligible to be activated.