In the short MTV advert, vampire hunk Edward Cullen, played by Pattinson, is seen standing at the altar, as his human bride-to-be Bella Swan, played by Stewart, walks up the aisle.
Stewart is only seen from the back while Pattinson is seen smiling as his fiancée approaches surrounded by guests at the wedding, which appears to be held in a forest.
Their Twilight co-star Elizabeth Reaser, who plays vampire matriarch Esme Cullen, said Pattinson was a bag of nerves shooting the scene with real-life girlfriend Stewart.
She told MTV: 'Well, the wedding scene was like a real wedding, in that it was stressful. It took a lot of planning, a lot of organisation. That was stuff we were all dealing with [and it was like] you were planning a real wedding.
'But it was really magical, and vampires aren’t supposed to cry, and that created a real obstacle for all of us vampires.
'Seeing Kristen walk down with aisle with [her on-screen dad] Billy Burke. I mean, seeing Billy Burke killed me.
She added: 'I understood in that moment what it’s like to be a parent and seeing Kristen and see her really be nervous and see Rob really, really be nervous, and the two of them [together with] the families coming together. It was an emotional day for real.'
MTV are set to broadcast the full clip during the MTV Movie Awards 2011 on Sunday, June 5.
Kristen Stewart is up for the Best Kiss award twice - she's been nominated for her smooches with Pattinson and Taylor Lautner.