Placido Polanco went 3-for-5 with an RBI for the Phillies, who led 3-1 for much of the game and then exploded for six runs in the ninth to blow it open.
Juan Pierre had a run-scoring single to touch off the big final frame, and Philadelphia salvaged one win in a three-game series against the Nationals.
Cole Hamels (4-1) notched his fifth straight start without a loss, limiting the Nationals to one run on five hits over eight innings. The left-hander walked one and struck out eight.
Jordan Zimmerman (1-3) absorbed the loss, yielding three runs on seven hits in a six-inning effort.