The 18-year-old 'Baby' hitmaker also won the night's first trophy for favourite Pop/Rock Male Artist and the favourite Pop/Rock Album prize, reported Ace Showbiz.
Dragging his reluctant mother Pattie Mallette up onstage with him, the pop superstar said, "This is my mom, she's little but she's beautiful... I want to thank you for just always believing in me... This is amazing."
He also addressed the drama swirling around his personal life amid reports he and longtime girlfriend Selena Gomez have split up, telling fans, "As long as you guys keep believing in me... I want to always make you proud."
It was a great night for Bieber's musical family too - his mentor Usher and protege Carly Rae Jepsen both performed and took home awards.
Usher was named favourite Soul/R&B Male Artist and Jepsen beat One Direction to score the New Artist prize.
Other performance highlights were by The Wanted, Kelly Clarkson, Kesha, No Doubt, Christina Aguilera, Taylor Swift and Pink.
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South Korean pop sensation Psy closed the show with his international smash hit Gangnam Style and was joined onstage by MC Hammer for a mash-up of his catchy anthem and Too Legit to Quit.
Psy and dance music star David Guetta made history at the AMAs by winning the first ever New Media Award and favourite Electronic Dance Music Artist honours, respectively.
There was also a tribute to the late Dick Clark, who created the American Music Awards.
The music and TV mogul's longtime friend Stevie Wonder took to the stage to perform a three-song medley of hits as images of Clark were beamed onto a screen behind him.