Mann will play a character who meets De Niro’s comedian unexpectedly at a wedding and the pair develop a close bond.
The project, which hails from Cinelou, has been a passion project for De Niro for years, previously having Mike Newell attached to direct. The script was penned by Art Linson with comedian Jeffrey Ross assisting with the stand-up routines.
Mann most recently starred in Vacation as Audrey (Griswold) Crandall and will next be seen in the upcoming How To Be Single opposite Dakota Johnson and Rebel Wilson.
She is repped by CAA.