Upton's HR in 10th lifts Braves past Nationals 3-2
Upton's 23rd homer to left-center came on a 2-2 pitch from Ian Krol (1-1).
Scott Downs (2-0) pitched a scoreless 10th for Atlanta.
Washington's Bryce Harper was hit by pitches in the fourth and eighth innings. Home plate umpire Marty Foster warned both benches after Luis Avilan hit Harper on his shoulder in the eighth.
Washington's players rose to the top of the dugout but didn't come onto the field.
The Braves, who swept a three-game series at Washington on Aug. 5-7, lead the season series 11-3, including six straight wins.