Apatow will write and direct the untitled project, which is currently scheduled to start production later this year in time for a June 1, 2012 release.
While the logline remains a mystery, it will be great to see Rudd and Mann playing off each other on the big screen again, as the duo shared fantastic chemistry as the quarrelsome couple in "Knocked Up." Mann played Katherine Heigl's sister in the $200 million-grossing comedy, and it's still unclear whether Heigl or co-star Seth Rogen will reprise their roles, though Heigl has called out Apatow in the past for his portrayal of women.
Mann is married to Apatow and has co-starred in all three of her husband's movies, while Rudd has popped up in several Apatow-produced comedies, although he did not appear in the filmmaker's last directorial effort, 2009's "Funny People."
Both Rudd and Mann have films at this month's Sundance Film Festival, as Rudd stars in "My Idiot Brother," while Mann appears in Elgin James' "Little Birds."
Mann is represented by CAA, while Rudd and Apatow are repped by UTA.
The duo's casting in Apatow's next movie was first reported by Variety.