Washington rallied twice from one-run deficits, and won with a Jayson Werth walkoff as the Nats knocked off the Chicago Cubs, 5-4, in 12 innings, on Wednesday.
The Nationals (41-24) took the three-game series from the Cubs (44-20), who dropped a series for just the fourth time this season.
Washington took a 2-1 lead with a Stephen Drew (.246/.301/.554) pinch-hit homer in the eighth, his sixth of the season, but the Cubs rallied in the ninth with a two-run Anthony Rizzo homer off Nats reliever Oliver Perez to go up 3-2.
Wilson Ramos (.335/.382/.553) tied it with two outs in the ninth, singling to center to score Bryce Harper from second.
Chicago took a 4-3 lead in the top of the 12th on an Addison Russell RBI single.
Danny Espinosa (.220/.313/.402) got on base with one out in the bottom of the 12th when he was hit by a pitch from Trevor Cahill (0-2, 2.83 ERA). Espinosa stole second and scored on an RBI single by Michael A. Taylor (.224/.261/.353).
Chris Heisey (.217/.309/.483) lined out to left for the second out, bringing up Werth (.248/.320/.439), who lined a shot off the top of the wall in center to score Taylor from first base, officially on a long single.
Yusmeiro Petit (2-0, 2.90) got the win in relief.
Starter Stephen Strasburg (10-0, 2.90 ERA) got a no-decision, giving up a run on six hits in seven innings, striking out eight and walking one.