The writer will conclude his run on the franchise in October with Fantastic Four #611 and FF #23.
Hickman revealed at Image Expo that he would be concluding his work on the two concurrent series, as well as on Ultimate Comics: Ultimates and S.H.I.E.L.D.
"I always had an end point in mind, but along the way I really fell in love with writing Marvel's First Family and I also had all these dangling bits to clean up, so I agreed - [and] wanted - to stay on," Hickman told Marvel.com.
"Then all the gears started turning on all the [Avengers vs. X-Men] stuff and what comes after and it just became obvious that October would be a good time to hop off."
Hickman has been working on Fantastic Four since 2009, launching FF during the original title's hiatus, which now runs alongside the core book.
He is also working on creator-owned Image Comics titles Manhattan Projects and Secret, and is co-writer on Marvel's upcoming Avengers vs. X-Men event miniseries.