The pair acknowledged their budding romance in 2011, after appearing arm-in-arm at that year's Cannes Film Festival and being spotted together throughout the fall of 2010. "I don't think it was planned one way or the other," McAdams said at the time about taking their romance public.
"Michael and I didn't get together while we were filming Midnight in Paris, which I feel strongly about not doing when I'm working. We became quite good friends, which I think is a great way to start," McAdams told The Sunday Telegraph's Stella magazine in January 2012. "I felt very blessed to have made a Woody Allen film in Paris together."
The Vow actress also shared that her most important relationship is good communication. "You need to trust each other and be able to talk to each other and be best friends."
During her relationship with the British actor, the paris remained steadfastly devoted to making it work. "Michael and I never spend more than three weeks apart -- we rack up a lot of air miles -- but you have to be quite adaptable in this business whether you are in a relationship or not," she told Stella.
McAdams, 34, will next star in About Time, about a man who travels back in time. She turned heads when photos from the set showed her in full-on baby bump mode, wearing a pregnancy prosthesis.
British actor Sheen, 45, was previously in a long-term relationship with actress Kate Beckinsale, and is the father of their daughter, Lily, 14. McAdams had been previously involved with Ryan Gosling.