The Biebs had already claimed the night's first trophy for Favorite Pop/Rock Male Artist and the Favorite Pop/Rock Album prize when his name was called as will.i.am presented the ceremony's last category.
Dragging his reluctant mum Pattie Mallette up onstage with him, the pop superstar said, "This is my mom, she's little but she's beautiful... I wanna 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 wanna always make you proud."
Watch Justin's performance:
Usher was named Favorite Soul/R&B Male Artist and Jepsen beat One Direction to score the New Artist prize.
Other performance highlights came from The Wanted, Kelly Clarkson, Ke$ha, No Doubt, Christina Aguilera, Taylor Swift and Pink, who recreated her dramatic performance dance video for Try onstage at the Nokia Theatre, while Psy closed the show with his international smash hit Gangnam Style - and a special guest.
The South Korean pop sensation was joined onstage by MC Hammer for a mash-up of his catchy anthem and "Too Legit to Quit."
Check it out:
Psy and dance music star David Guetta made history at the AMAs by winning the first ever New Media Award and Favorite Electronic Dance Music Artist honors, respectively.
There was also a tribute to the late Dick Clark, who created the American Music Awards. The music and TV mogul's longtime pal Stevie Wonder took to the stage to perform a three-song medley of hits as images of Clark, who died in April, were beamed onto a screen behind him.
The 2012 AMA winners are:
Favorite Adult Contemporary Artist - Adele
Favorite Contemporary Inspirational Artist - tobyMac
Favorite Latin Music Artist - Shakira
Favorite Pop/Rock Band/Duo or Group - Maroon 5
Favorite Pop/Rock Female Artist - Katy Perry
Favorite Soul/R&B Album - Talk That Talk by Rihanna
Favorite Soul/R&B Female Artist - Beyonce
Favorite Pop/Rock Male Artist - Justin Bieber
Favorite Female Country Artist - Taylor Swift
New Media Award - Psy
Favorite Rap/Hip-Hop Album - Pink Friday: Roman Reloaded by Nicki Minaj
Favorite Alternative Rock Artist - Linkin Park
Favorite Soul/R&B Male Artist - Usher
Favorite Country Male Artist - Luke Bryan
New Artist of the Year - Carly Rae Jepsen
Favorite Country Band/Duo or Group - Lady Antebellum
Favorite Electronic Dance Music Artist - David Guetta
Favorite Pop/Rock Album - Believe by Justin Bieber
Favorite Rap/Hip-Hop Artist - Nicki Minaj
Favorite Country Album - Blown Away by Carrie Underwood
Artist of the Year - Justin Bieber
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