It was the eighth straight win for the Warriors, the last four having come on a seven-game road trip that has stops remaining in Washington, Milwaukee and Brooklyn.
Golden State trailed by 15 points with 6:48 to play after Atlanta's Pero Antic hit a 3-pointer and the Warriors were still four points behind in the closing minute.
That shot misfired and Iguodala grabbed the rebound. After a time out, the ball went to Iguodala and he came through with the fifth buzzer-beating shot since he entered the NBA nine years ago.
Iguodala finished with seven points after going scoreless through the first three periods.
David Lee led the Warriors with 23 points and eight rebounds. Curry had 22 points, eight boards and nine assists.
Antic had 16 points to lead Atlanta.