The actresses attended a photocall for Café Society at the Cannes International Film Festival, walking the red carpet with the movie's director, Woody Allen.
Stewart, 26, who sported freshly dyed platinum blonde hair, wore a white Chanel crop top with matching skirt and print Christian Louboutin pumps. Lively, 28, wore a red Juan Carlos Obando jumpsuit.
Café Society was to open the film festival Wednesday evening before its release in theaters July 15. The romantic comedy takes place in the Golden Age of Hollywood and co-stars Steve Carell, Jesse Eisenberg and Parker Posey.
"I needed someone who could play an adorable little secretary from Nebraska, [and then] later in the movie you could see her in furs and jewels, and she would look just smashing and elegant," Allen told reporters of Stewart's casting.
"She's very young, very beautiful and talented," he previously said of the actress to Variety. "And if she just keeps her hand on the wheel and makes good decisions, she's home free. She should have an incredible career."
Café Society's premiere follows fresh criticism from Allen's son Ronan Farrow in an essay for The Hollywood Reporter. Ronan slammed the media and the director's collaborators following sister Dylan Farrow's allegations that Allen abused her as a child.
"The old-school media's slow evolution has helped create a culture of impunity and silence," Ronan Farrow wrote, suggesting the media hasn't given due attention to his sister's claims. "Actors, including some I admire greatly, continue to line up to star in his movies."
"[Stewart and Lively] can trust that the press won't ask them the tough questions," he said. "That kind of silence isn't just wrong. It's dangerous. It sends a message to victims that it's not worth the anguish of coming forward."
Stewart said she questioned working with Allen in the May issue of Variety, but said "the experience of making the movie was so outside of that, it was fruitful ... to go on with it." The actress also discussed dating women in the interview, explaining she won't label or define her sexuality.