The makeup date was not announced at the time of the postponement Saturday.
The series between the NL East rivals is scheduled to conclude Sunday with the All-Star pitching matchup of Mike Foltynewicz (7-5, 2.66) against Max Scherzer (12-5, 2.41). That game is to start 1:35 p.m., though rain is forecast.
Braves pitcher Sean Newcomb (8-5, 3.51 ERA) and the Nationals' Gio Gonzalez (6-6, 3.72) were Saturday's scheduled starting pitchers.
The Braves, battling Philadelphia for the division lead, beat Washington 8-5 on Friday. Washington fell to 48-49 with the loss and has dropped three of four games.
Scherzer, who started the All-Star game Tuesday night at Nationals Park, engaged in a heated spat with fellow starter Stephen Strasburg in the dugout during Friday night's defeat.
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