In the second inning at Nationals Park, Stanton took the ball deep to right-center off Nationals veteran Livan Hernandez. After the ball bounced back into the field of play, Stanton sprinted to third with what initially would have been an RBI triple.
Immediately, Marlins manager Edwin Rodriguez asked the umpires to review whether the ball was out of the park. Home plate umpire Mike Winters got with crew chief Jerry Layne, and the four umpires headed off the field to check instant replay.
It didn't take long for them to return. Winters informed Nationals manager Jim Riggleman, and then signaled home run. Stanton trotted home with what was scored a two-run homer that gave Florida a 2-0 lead.
After matching a franchise record by collecting five hits on Wednesday night, Stanton's homer marked his sixth consecutive hit.
Stanton now has 12 home runs -- and he is approaching the rookie home run leaders in far fewer games. He reached 12 homers in his 190th at-bat.
Called up from Double-A Jacksonville on June 8, Stanton was playing his 53rd big league game. Tyler Colvin of the Cubs, through 104 games, paces all rookies with 18 homers.