The comediennes will join the cast that already includes Rafe Spall and Simon Baker.
The film is about a mismatched couple trying to get through their first year of marriage. Byrne and Spall will be playing the married couple and the others will be the supporting characters.
Byrne appeared in the blockbuster films “X-Men: First Class” and “Bridesmaids” last year. She is currently on a crime drama television series “Damages.”
And Faris was known for several comedic films, including the “Scary Movie” series, “What’s Your Number?” and “The House Bunny.” She will be appearing in “The Dictator” and “Movie 43” later this year.
The film is being written and directed by Dan Mazer (“Bruno”).