The 31-year-old actor and 34-year-old actress attended the Toronto International Film Festival premiere of Bell's movie Film Stars Don't Die in Liverpool two months after their wedding.
Bell, who plays actor and author Peter Turner in the film, kept an arm around Mara's waist as they posed for photos. The actress wore metallic pumps and a white minidress with a high neck and ruffle detail.
Bell's co-star Annette Bening also walked the red carpet with her husband, Warren Beatty. The longtime couple married in March 1992, and share four children, sons Stephen and Benjamin and daughters Isabel and Ella.
"I like 'respect,'" Bening said in an interview with Today in December of the secret to her relationship with Beatty. "But also I think in some ways we're very different, some ways we're alike. But the differences, I think, help us and there's some fire there."
"We want the same things; we have four children and they're incredible human beings," she added. "Having that shared purpose also is part of it."
Bell and Mara tied the knot in July after two years of dating. The actress confirmed the news on Instagram by sharing a photo from her wedding reception.
"Nuptials," she wrote at the time.