The country singer was picking up the award for 'Best Female Video' for 'You Belong With Me' when the rapper appeared onstage and took her microphone.
"Taylor, I'm really happy for you, I'm gonna let you finish, but Beyoncé had one of the best videos of all-time," he announced. "One of the best videos of all-time!"
Beyoncé, who had been nominated in the category for 'Single Ladies', was seen shaking her head while Swift stood silently. The crowd then began to boo, prompting West to leave the stage.
According to MTV, West displayed his middle finger to the audience before returning to his seat and kissing girlfriend Amber Rose.
More from the VMAs:
> Winners list in full
> GaGa 'bleeds' onstage in VMAs performance
> Watch the latest 'Twilight: New Moon' trailer
> Summary: Who won big at the VMAs?
> Madonna's teary Jackson tribute
> GaGa kisses Kermit on red carpet