New York trailed by a run heading into the ninth and appeared set to waste a complete-game performance by Ivan Nova.
Ichiro Suzuki put down a sacrifice bunt that moved the runners to second and third and Robinson Cano was walked intentionally to load the bases. Johnson next walked Travis Hafner on four pitches to force in the tying run and Wells came through with his base hit to left-center that gave the Yankees their fifth straight victory.
Matt Wieters hit a two-run homer in the second and that blast almost stood up for the Orioles.
Nova (3-2) went the distance for the first time in 68 career starts, allowing three hits with one walk and 11 strikeouts. Nova, however, hit Chris Davis with a pitch leading off the second and then gave up a homer to Wieters on a 1-1 pitch.