Miami is 12-3 this month after a slow 8-14 start in April. The Marlins (20-17) moved three games over .500 for the first time this season.
The Marlins led 6-1 off struggling Braves left-hander Mike Minor before Atlanta scored three runs off Mark Buehrle in the sixth. Stanton’s eighth homer, which drove in Kearns after his second double, pushed the lead to 8-4 in the seventh.
Buehrle (3-4) gave up four runs on six hits in six innings with the win in the first meeting of the season between the NL East rivals.
Austin Kearns and Emilio Bonifacio each had two hits and drove in two runs. Omar Infante had two hits and scored two runs.
Minor (2-3) gave up six runs on six hits in 4⅔ innings, the fourth consecutive start he has allowed six or more runs. He gave up three runs in the fourth and three more in the fifth, leaving his ERA at 7.09 and his spot in the rotation on possibly shaky ground.
Stanton might have saved two runs by making a strong catch in right field.
With Miami leading 3-1 in the fourth, the Braves had runners on second and third with two outs following singles by Dan Uggla and Brian McCann. Jason Heyward hit a drive that looked like a sure two-run double before Stanton, running at full speed toward the foul line, made a diving catch. Stanton landed about one foot in front of the warning track.
Minor’s slump leaves his spot in the rotation in possible jeopardy. Possible options for the Braves include Livan Hernandez and Kris Medlen, who could move from the bullpen, and Julio Teheran at Triple-A Gwinnett.
Kearns had a two-run double in the Marlins’ three-run fourth. Minor was knocked out of the game after giving up three hits, including a run-scoring single by Gaby Sanchez, in the fifth. Bonifacio added his second RBI single of the game.
Rookie shortstop Tyler Pastornicky hit leadoff for the first time as Braves manager Fredi Gonzalez rested centerfielder Michael Bourn.
Pastornicky, the normal No. 8 hitter, led off the first with a single, moved to third on Martin Prado’s double and scored on Freddie Freeman’s groundout to first base.
Buehrle retired 10 straight batters after the double by Prado, who had three hits.
Heath Bell pitched the ninth in a non-save situation for Miami.
NOTES: Heyward made his first career start in centerfield. ... The Marlins’ record for wins in May is 16 in three seasons, most recently 2008. ... Bourn popped out to left field as a pinch-hitter in the ninth. ... Freeman returned after missing one game with a scratch on his right eye. ... RHP Ricky Nolasco will attempt to take sole possession of the Marlins’ record for career wins when he faces RHP Brandon Beachy (4-1), who leads the major leagues with his 1.60 ERA, on Thursday night. Nolasco (4-1) is tied with Dontrelle Willis at 68 wins.