The Bridesmaids star is being eyed for the role of an employee at Paul Rudd's character's indie record company, according to Variety.
Rudd, Leslie Mann and Charlyne Yi will appear again, alongside newcomers to the cast such as Albert Brooks, Lena Dunham and Megan Fox.
Wyatt Russell, who will next be seen in Cowboys and Aliens, is also in negotiations for a role in the Judd Apatow comedy.
During a Twitter interview with Digital Spy, the IT Crowd actor said that he preferred comedic roles to dramatic, also finding them more challenging.
"I prefer comedy because I love the sound of children laughing and the money's better," he quipped.
However, O'Dowd recently revealed that he intended to be a "straight" actor before landing a comic role in the period drama Vera Drake.
> Chris O'Dowd's Twitter chat with Digital Spy in full