The "Twilight" starlet will play "Valentin" in the film, which tells the story of an aging actress (Binoche) who returns to the theater for the revival of a play that made her famous, except that this time she plays opposite to the young role she once had.
Stewart will play Binoche's assistant and Chloe Grace Moretz will play the young actress who has Binoche's former role.
"It takes two very particular people to have that relationship be functional -- one that services the other -- because Juliette Binoche is playing the actress that I assist, and she is one of the most powerful women I think I've ever seen in film," Stewart told WWD in July. "I'm going to try desperately to not be squashed by a woman like that, and it's not going to be an easy thing."
Funny enough, Binoche starred opposite to Stewart's former boyfriend, Robert Pattinson, in the 2012 film "Cosmopolis."
Directed by Olivier Assayas, "Sils Maria" is due in theaters some time in 2014.