The "Friends" star and "Without a Trace" actress joined the cast of Susan Sarandon and her daughter Eva Amurri Martino, Sharon Stone, Christina Ricci and Paul Wesley.
The film, which will be co-directed with Nigel Levy from a script by Paige Cameron, is about a photographer whose life is changed forever by an unexpected pregnancy.
The film is produced by Danielle James and Amy Williams.
While Cox just wrapped her sixth season on "Cougar Town", Sanchez is on the Lifetime show "Devious Maids," which is in production on its third season.