At least 12 people, including one alleged gunman, were killed and several others injured in a shooting at the Navy Yard, a government installation about a half mile from the U.S. Capitol.
Nationals Stadium is also near the shooting site. The main Metro station for the ballpark is the Navy Yard Station and the main parking lot in the area was being used by officials in the shooting investigation.
Baseball officials said the postponed game would be made up Tuesday as part of a day-night doubleheader.
The division-leading Braves have a 10-game lead over the Nationals for first in the National League East, Washington is 4 1/2 games out in the NL wild-card race.