Adam LaRoche homered and drove in four runs and Edwin Jackson earned a win for the first time since mid-April as the Nationals edged the Mets, 5-3.
Jackson (2-3), winless in his previous eight starts, allowed three runs -- two earned -- on three hits and four walks over seven frames.
"He was exceptional for us tonight," said Washington manager Davey Johnson about Jackson. "Seven strong innings and he probably had a little bit left in the tank."
Michael Morse went 2-for-3 with an RBI for Washington, which had lost four of five before taking the first two meetings of this three-game set.
Jeremy Hefner (1-3) took the loss after allowing four runs -- three earned -- on seven hits in six innings of work.
"I just didn't get it done and didn't execute my pitches," said Hefner. "They were hitting balls hard in those first three innings. I thought I did a little better in the later innings."
New York recorded just three hits in losing its third straight game.
The Nationals got to Hefner early, as LaRoche smacked a three-run homer in the first inning. Bryce Harper reached on an error and Ryan Zimmerman worked a walk prior to the first baseman's ninth round-tripper of the year.
Kirk Nieuwenhuis singled in a run in the away third, and David Wright scored on a Lucas Duda groundout in the fourth, cutting the Mets' deficit to 3-2.
Washington got a run back in the fourth on Morse's RBI single to right, and the teams traded runs in the seventh.
Ike Davis doubled leading off the top half and eventually scored on an Omar Quintanilla groundout before LaRoche's sacrifice fly to center chased home Steve Lombardozzi in the bottom half.
Sean Burnett pitched a perfect eight for Washington, and Tyler Clippard stranded a runner on second in the ninth to record his fifth save.
LaRoche's homer and Davis' double were the only extra-base hits in the game...Hefner got the start in an effort to provide some extra rest for Johan Santana, who unleashed a career-high 134 pitches in Friday's no-hitter against the Cardinals. Santana will pitch on Friday versus the Yankees, with R.A. Dickey staying on regular rest to pitch Thursday's finale with the Nats, who will counter with Chien-Ming Wang...The Mets activated Jason Bay from the disabled list before the game, but the outfielder did not play. Bay has been sidelined since April 24 due to a fractured left rib.