Both chapters are scheduled to air back-to-back Feb. 20. Wilson will play a cult leader in 1980s Oregon, while Zadegan will be his assistant and Keaton portrays the FBI agent who tries to bring the enterprise down.
"After years of trying to start a cult of our own, we have happily outsourced the heavy lifting to the brilliant team behind Documentary Now! and they have, as always, delivered," IFC Original Programming SVP Christine Lubrano said in a statement. "Seeing these episodes have caused the IFC staff to zealously follow the teachings of Owen Wilson."
Keaton is also known for his roles in Spider-Man: Homecoming, Birdman, Spotlight, Batman, Johnny Dangerously and Mr. Mom.
Wilson's credits include the Zoolander and Night at the Museum movies, as well as The Royal Tenenbaums and The Life Aquatic with Steve Zissou.