BIEBER fever broke out at the American Music Awards with the teenager dominating proceedings.
"I wanted to thank you for always believing in me," the young star said addressing his mother.
The 18-year-old also won the honour in 2010. He said it's "hard growing up with everyone watching me" and asked that people continue to believe in him.
"Wow. I feel violated right now," he said, laughing.
"I did grab his butt," McCarthy said backstage.