Portman, 25, makes a cameo as a ghost in the video for "Dance Tonight," a track from McCartney's new studio album, "Memory Almost Full." The video had its world premiere Wednesday on YouTube.com.
"The connection with Natalie came from my daughter Stella, who makes non-leather shoes that Natalie buys, so I just thought, `Well, I'll ring her up and just see if she'll do it.' So I rang her up and said, `Hey, I'm Stella's dad!"' the 64-year-old former Beatle said in a statement posted on his Web site.
Portman, whose screen credits include the new "Star Wars" trilogy, "Closer" and "V for Vendetta," plays a "futurist electronic ghost" who is summoned by the sound of McCartney's mandolin.
Filmmaker Michel Gondry ("Eternal Sunshine of the Spotless Mind") directed the video.
"Memory Almost Full," McCartney's 21st solo album, will be released June 5 in the United States. It is his first release for Hear Music Starbuck Corp.'s new record label.
McCartney last released the acclaimed "Chaos and Creation in the Backyard," in 2005.