The comedian and the "Knocked Up" director have cowritten what's being described as "a semi-autobiographical story of Davidson growing up in Staten Island, New York."
Besides dating Ariana Grande and becoming one of the youngest comedians on "SNL," Davidson was known early on for his stand-up about the biggest tragedy in his life: Losing his father at age 7 in the 9/11 attacks.
Production is scheduled to begin in May or June.
Davidson is earning praise for "Big Time Adolescence," which premiered Monday at the Sundance Film Festival to strong reviews. He also makes an appearance in "What Men Want," which opens February 8.
The as-yet-untitled project will be Apatow's first feature since 2015's "Trainwreck" starring Amy Schemer. He won an Emmy for the documentary "The Zen Diaries of Garry Shandling," about his late mentor.