He went 1-for-4 in the Nationals' 5-2 victory, which ended Washington's season-worst four-game losing streak and returned the Nationals to .500 at 25-25 this season.
LaRoche had been out since May 10 with a strained right quadriceps before rejoining the lineup Sunday. He is hitting .316 with five home runs and 21 RBIs in 33 games.
The Nationals had hit just .194 during their season-worst four-game losing streak that had dropped them under .500 for the first time this season.
Washington optioned rookie infielder Zack Walters to Triple-A Syracuse after Saturday's 3-2 loss to the Pirates to clear a roster spot for LaRoche. Walters hit .182 with three homers in 27 games.
The Associated Press contributed to this report.