The homer, the third of the game for Atlanta, was Kemp's seventh game-ending shot of his career.
Gearrin (1-2) walked Nick Markakis with one out before Kemp's homer barely cleared the right field wall..
Matt Adams hit a two-run homer and Tyler Flowers also homered off Jeff Samardzija.
Braves Sean Newcomb, who gave up one run in six innings, was denied his first win when Hunter Pence's homer off Braves closer Jim Johnson tied the game at 3-3 in the ninth. It was Johnson's fifth blown save in 18 chances.
