The Nats got another good performance from veteran pitcher Livan Hernandez (4-1), who allowed only one earned run on five hits and five walks over 5 1/3 innings. Hernandez has allowed two runs or fewer in each of his five outings this season.
Matt Capps got the final two outs in the ninth to rack up his 11th save of the year.
Jason Heyward smacked a solo homer and walked twice for the Braves, who dropped their eighth straight road game.
Atlanta starter Kenshin Kawakami dropped to 0-5 after yielding three runs on seven hits over five innings.