For the second straight night, the Nationals and Braves played extra innings, but this time it was Atlanta that came away with the victory, 6-5 in 10 innings.
The Nationals blew a four-run lead en route to the extra-inning loss.
Atlanta catcher Brian McCann drove home the winning run, lining a Doug Slaten pitch to right field, scoring Martin Prado. Prado played the hero earlier in the game when he hit a grand slam in the seventh inning to tie the score at 5.
The loss spoiled the effort of Nationals starting pitcher Jordan Zimmermann who struck out a career high 11 batters, while limiting the Braves to one run over 6 1/3 innings.
Washington jumped out to an early 5-1 lead thanks in part to home runs by Danny Espinosa and Ivan Rodriguez.
The Nationals return home Friday to begin a three-game series with the Florida Marlins. Tom Gorzelanny will make the start for Washington, while Florida will counter with Chris Volstad.