"If we are the No. 1 movie in America, I will do a Calvin Klein underwear campaign," Kutcher said in an interview on syndicated entertainment show "Access Hollywood," which aired Tuesday night.
"It's actually a bet that I made with my producing partner, so we will see what happens," he added.
Kutcher has modeled for clothing lines, including magazine ads for Calvin Klein and catwalk work for Versace.
He co-stars with Amanda Peet in "A Lot Like Love." Opening Friday, the romantic comedy's competition for No. 1 at the box office will likely come from new release "Kung Fu Hustle" and last week's top earner, "The Amityville Horror."
Posing in underwear wouldn't seem to be an issue for the 27-year-old actor, who had no trouble doing his first nude scene in "A Lot Like Love."
"I like being nude," he said. "So for me, it wasn't incredibly tough."