The 18-year old beat the likes of Katy Perry, Drake, RihannaandMaroon 5 to the coveted Artist of the Year Award - lifting his mum Pattie Mallette up the air after his name was read out, as he invited her to join him on stage.
JB was clearly taken back by his win, struggling to get his words out during his acceptance speech.
He said: "This is my mum, this is my mum. She's little, but she's beautiful. And thank you so much. First of all, I wanna say... they told me to... I can't even think, I mean, I'm so blown away right now."
Bieber then turned to Mallette and said: "I want to thank you for just believing in me. I want to thank everyone, just everyone. I'm at a loss for words.
"I just want to say... it's hard growing up with everything going on, with everyone watching me. I just wanted to say that as long as you guys keep believing in me, you know, I will never... I will always make you proud.... So thank you so much. I love you."
The Boyfriend singer also took home trophies for Favourite Male Artist - Pop/Rock and Favourite Album - Pop/Rock for Believe.
His Beauty And A Beat collaborator Nicki Minajalso won two awards for Favourite Album - Rap/Hip-Hop for Pink Friday: Roman Reloaded and Favourite Artist - Rap/Hip-Hop.
In her speech for the latter prize, Minaj stated: "Barbz, I know you're somewhere out there watching this on TV. I love you so much, you are so passionate and inspiring.
"Thank you so much for voting your little fingers off... I've got to thank anyone who had anything to do with my career ever."
Nicki then thanked her continued her best friend Taeisha, her hairdresser Terence, "who I never thank", Lil Wayne and her label Young Money Entertainment, before adding: "Thank you to the AMAs, you guys always have the best shows."
However, it was PSYwho stole the show yet again, this time, teaming up with MC Hammer for a rendition of his smash hit single Gangnam Style mashed with the rapper's tune 2 Legit 2 Quit to close the bash - with the pair both wearing 'Hammer pants.'
Full list of 2012 AMA winners:
Artist of the Year Justin Bieber - WINNER Drake Maroon 5 Katy Perry Rihanna
New Artist of the Year J. Cole fun. Gotye Carly Rae Jepsen - WINNER One Direction
Favourite Male Artist - Pop/Rock Justin Bieber - WINNER Flo Rida Pitbull Usher
Favourite Female Artist - Pop/Rock Kelly Clarkson Nicki Minaj Katy Perry - WINNER Rihanna
Favourite Band, Duo or Group - Pop/Rock fun. Maroon 5 - WINNER One Direction The Wanted
Favourite Album - Pop/Rock Justin Bieber - Believe - WINNER Maroon 5 - Overexposed Nicki Minaj - Pink Friday: Roman Reloaded One Direction - Up All Night
Favourite Male Artist - Country Jason Aldean Luke Bryan - WINNER Eric Church
Favourite Female Artist - Country Miranda Lambert Taylor Swift - WINNER Carrie Underwood
Favourite Band, Duo or Group - Country Zac Brown Band Lady Antebellum - WINNER Rascal Flatts
Favourite Album - Country Luke Bryan - Tailgates & Tanlines Lionel Richie - Tuskegee Carrie Underwood - Blown Away - WINNER
Favourite Artist - Rap/Hip-Hop Drake Nicki Minaj - WINNER Tyga
Favourite Album - Rap/Hip-Hop J Cole - Cole World: The Sideline Story Drake - Take Care Nicki Minaj - Pink Friday: Roman Reloaded - WINNER
Favourite Male Artist - Soul/R&B Chris Brown Trey Songz Usher - WINNER
Favourite Female Artist - Soul/R&B Beyoncé - WINNER Mary J Blige Rihanna
Favourite Album - Soul/R&B Chris Brown - Fortune Rihanna - Talk That Talk - WINNER Usher - Looking 4 Myself
Favourite Artist - Alternative Rock The Black Keys Gotye Linkin Park - WINNER
Favourite Artist - Adult Contemporary Adele - WINNER Kelly Clarkson Train
Favourite Artist - Latin Don Omar Pitbull Shakira - WINNER
Favourite Artist - Contemporary Inspirational Jeremy Camp Newsboys tobyMac - WINNER Favourite Artist - Electronic Dance Music (EDM) David Guetta - WINNER Calvin Harris Skrillex