Avilan, who began the season as one of Atlanta's top setup relievers, is with the team for Thursday's game against the Los Angeles Dodgers.
Avilan was 3-1 with a 4.85 ERA in 47 games when he was optioned to Gwinnett on July 19. He says he focused on his curveball and change-up at Gwinnett.
Avilan joins James Russell as left-handers in the Braves' bullpen.
The Braves relied on Avilan in 2013, when he was 5-0 with a strong 1.52 ERA in 75 games.
The Braves optioned right-hander Juan Jaime to Gwinnett following Wednesday night's win over the Dodgers.