The Can't Feel My Face star beat out the likes of D'Angelo and Chris Brown for the prize, in recognition of his chart-topping record, Beauty Behind the Madness.
He was handed his first-ever American Music Award by music icon Prince, who took the stage to present the trophy with a guitar strapped across his chest.
Jennifer Lopez, who is also serving as the ceremony's host, kicked off the show at Los Angeles' Microsoft Theatre by singing her hit Waiting for Tonight, before going into a dance routine featuring the music of Beyonce, Bruno Mars and Rihanna, among others.
Other performers are set to include Justin Bieber, Ariana Grande, Demi Lovato, Coldplay, Gwen Stefani, One Direction, and Celine Dion.
Taylor Swift leads all nominations with six, just ahead of her pal Ed Sheeran and The Weeknd, who trail behind with five.