With the Mets down by a run entering their final at-bat, Ike Davis led off with a double off John Axford (8-2). One out later Josh Thole singled, sending Davis to third. Tejada followed with a blast to left center, chasing home the game-winning runs.
The rally made a winner of Elmer Dessens (4-2) and allowed the Mets to take the first contest of a four-game set at Citi Field.
New York starter Mike Pelfrey went 7 1/3 innings, allowing three runs on five hits and David Wright smacked his 27th homer of the year.
Brewers starter Randy Wolf went seven innings, allowing a pair of runs on four hits.