McAdams, 34, and Sheen, 44, took their romance public in October 2010 after meeting on the sets of Woody Allen's film.
"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. I felt very blessed to have made a Woody Allen film in Paris together," McAdams had said earlier.
The 'Vow' actress also shared that her most important relationship is good communication.
The Canadian star's last serious relationship prior to Sheen was with her Notebook costar Ryan Gosling. The two began dating in 2005 and were briefly engaged, but called it off in 2007.
Sheen had an eight-year relationship with actress Kate Beckinsale from 1995 until 2003; the two share daughter Lily, 14.