Toronto snapped a two-game skid and climbed back a game above .500.
Arencibia scored a run in the first on a wild pitch while the Blue Jays were building a 3-0 advantage and then provided the game's key blow in the fifth.
Zach Britton loaded the bases on two walks and a single when Arencibia came to the plate with two away. He fell behind in the count 1-2 before launching a shot to left for his ninth homer of the season.
Britton (5-4) was held to the shortest outing of his rookie season. He gave up seven runs on six hits in five innings.
Carlos Villanueva (3-0) picked up the win by lasting 5 1/3 innings, during which he allowed two runs on six hits.
The Orioles, who lost for the sixth time in seven contests, opened a nine-game homestand.
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