The pop rock band, consisting of sisters Este, Danielle and Alana Haim, performed its song "3 AM" on the NBC late-night talk show Thursday.
Pattinson, who played vampire Edward Cullen in the Twilight movies, appeared via video call at the beginning of the performance. The actor played an "emotional vampire" ringing for a booty call.
"Hey, what's up? Just calling to see if you're still up, but it went straight to voicemail. That's too bad. If you're up or whatever, then you know where to find me. Bye," he says.
Haim wore white wedding gowns, veils and bloody makeup to perform "3 AM," which appears on the group's album Women in Music Pt. III.
During the Late Night interview, the members of Haim discussed how Pattinson's cameo came about. The sisters said they wanted to cast someone British to match the voice on the record.
"In the end, the person that won the part was Robert Pattinson," she added. "He's the best. We love him. He really did us a solid by doing this."
Haim released Women in Music Pt. III, its third studio album, in June. The album features several singles, including "Summer Girl," "Now I'm in It" and "Don't Wanna."