The actress donned a floorlength Yves St Laurent black gown while Pitt opted for a black suit with a T-shirt.
The couple smiled and posed for cameras together as the crowd cheered for Jolie and lavished her with get well soon gifts.
Jolie, 37, talked about her preventive double mastectomy in a New York Times op-ed piece last month. Pitt supported her decision by calling it "heroic". The actress, whose mother died of cancer, opted for the operation after learning that she carried a faulty gene.
"I'm very, very grateful for all the support. I've been very happy just to see the discussion about women's health expanded, and that means the world to me."
The premiere was also attended by Pitt's co-stars Mireille Enos and Peter Capaldi, director Marc Forster, executive producer David Ellison, son of Oracle founder Larry Ellison and CEO of Skydance, and celebrity guests Idris Elba, Tom Ford, Rita Ora and British band Lawson.