The Hollywood actor plays guitar on the group's upcoming album Music from Another Dimension! and he joined them for a special performance during their show at the Hollywood Bowl.
Frontman Steven Tyler introduced the star to the stage, telling the crowd, "I need a little help up here. Johnny Depp, are you in the house?"
Depp then walked on and played guitar on classic track Train Kept A-Rollin' for a crowd which included Tyler's actress daughter Liv and funnyman Jim Carrey.
After the gig, Depp joined the band for an afterparty at Mexican restaurant Pink Taco on the Sunset Strip with other famous faces including Alice Cooper and Breaking Bad star Aaron Paul, according to New York Post gossip column Page Six.