Chris Johnson, leading the National League in hitting with a .331 average, singled with one out in the 11th off Ryan Webb (1-5) and went to second on Brian's McCann's groundout.
Johnson also finished 4-for-6 for the National League East-leading Braves, who racked up a sixth straight win.
Luis Ayala (1-1) earned the win with a scoreless top of the 11th.
Justin Ruggiano cracked a two-run homer and Giancarlo Stanton added a solo shot for the Marlins.
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Aaron Carter is still in love with Hilary Duff