Dressed in a shimmery white leotard and a furry white vest, Cyrus went on to the stage to accept the best video award for her song "Wrecking ball".
"I don't think I'm going to be able to fit that in my purse so I'll put it right here for now," the 20-year-old said, before placing the award near her feet.
"I couldn't fit this award in my bag, but I did find this," she said, before pulling out the supposed joint.
She then proceeded to light it and take a long drag.
Cyrus performed on her track "We can't stop" twerking in a silver skin-tight dress at the event.