Radnor will direct and star in the film. The actor will play a 35-year-old still yearning for college life who must face his age and responsibilities in the follow-up to his 2010 movie, "HappyThankYouMorePlease."
Janney has signed on to play a cold English professor in a cast that also includes Elizabeth Olsen, Richard Jenkins and Elizabeth Reaser.
A release date for the film has not yet been announced.
Janney was nominated for a Tony Award in 1998 for her performance in A View From the Bridge and again in 2009 for her performance in 9 to 5. Radnor has been seen on Broadway in The Graduate.