Drake Baldwin had two hits, drove in two runs and scored twice for Atlanta.
Elder (3-1) pitched 6 2/3 innings, giving up four runs (three earned) on three hits. He struck out six.
Daylen Lile homered for the Nationals, who were held to three hits and fell to 2-8 at home.
Jake Irvin (1-3) allowed four runs (three earned) in five-plus innings.
Atlanta’s Ronald Acuna Jr. left the game in the sixth inning after being hit by an Irvin pitch for the second time. X-rays on Acuna’s left hand came back negative and the Braves said he is day-to-day.
The Nationals took a 2-0 lead in the first thanks to some patient at-bats. With two outs, Brady House singled and CJ Abrams and Lile worked walks to load the bases. Jacob Young lined a single to right, driving in House and Abrams.
Atlanta tied it in the fourth. Acuna was hit by a pitch leading off but was picked off first base. Baldwin singled and Olson homered to center to tie it.
Lile homered leading off the bottom half to make it 3-2.
The Braves took control with a five-run sixth. Mike Yastrzemski reached on a throwing error by Nasim Nunez. Acuna took his second HBP, and Irvin was lifted in favor of PJ Poulin. Both runners advanced on a wild pitch and scored when Baldwin doubled to left.
Austin Riley walked with one out and Brad Lord replaced Poulin. Ozzie Albies singled home Baldwin to make it 5-3, and Michael Harris II singled home Riley. Dominic Smith grounded back to the mound, but the Nationals could not turn two and another run scored to make it 7-3.
The Nationals got one back in their half when Abrams was hit by a pitch, stole second and scored when Young reached on third baseman Riley’s throwing error.
The Braves added two in the ninth on an RBI bunt single by Eli White and a sacrifice fly by Olson.
