Ethier hit a 1-2 pitch out to right off Rafael Soriano (1-2), bringing the Dodgers their seventh victory in nine games. The other Los Angeles runs came in the third on a homer by Hanley Ramirez against Stephen Strasburg.
Ethier's blast made a winner out of Ronald Belisario (4-5), who faced only one batter in the eighth inning and retired him on two pitches.
Kenley Jansen struck out two in a perfect ninth for his 10th save.
The Washington runs scored on a wild pitch in the second inning and an RBI single by Ian Desmond in the sixth.
Gal Gadot cast as Wonder Woman for 'Batman vs. Superman'
Beyonce flaunts bikini body, Blue Ivy in vacation pics