Former Playboy model, Jenny McCarthy presented the 18-year-old singer with the pop/rock album prize for his record Believe at the ceremony on Sunday night and she admits she couldn't resist giving the "delicious" star's rear a squeeze.
Speaking backstage at the AMAs, which took place at Los Angeles' Staples Center, she said, "I did grab his butt. I couldn't help it. He was just so delicious. So little. I wanted to tear his head off and eat it!"
Justin, who also picked up artist of the year and the pop/rock male artist gongs, was also kissed on the neck by 40-year-old Jenny as she gave him the award.
He laughed in response and said, "Wow. I feel violated right now!"
Jenny later posted a picture of the kiss on twitter and wrote: "Cougar rape #poorjustin (sic)"
The Boyfriend hitmaker , who was accompanied to the event by his mother Pattie Mallette, later admitted the evening had been one he would never forget.
He tweeted: "Loss for words tonight. Like i said as long as you BELIEVE in me i will always try to make you proud. Thank you. tonight i will never forget (sic)"
Despite recently splitting from girlfriend Selena Gomez, it has been claimed that Justin was seen backstage holding hands with the 20-year-old beauty.
According to E! News, Selena arrived at the end of the show to meet with the Never Say Never star after the ceremony.