Hunnam was set to star as Christian in the film, based on the erotic best-seller of the same name, alongside Dakota Johnson as Anastasia.
"The filmmakers of 'Fifty Shades of Grey' and Charlie Hunnam have agreed to find another male lead given Hunnam's immersive TV schedule, which is not allowing him time to adequately prepare for the role of Christian Grey," Universal Pictures said in a statement.
Production on the film was scheduled to begin in the first of November in Vancouver, shortly after the end of production on the current season of "Son's of Anarchy" on Oct. 21, The Hollywood Reporter said Saturday.
Sources told the entertainment industry publication that Hunnam got cold feet about being involved in such a high-profile project. They said he didn't have reservations about playing the role, but was concerned about the media and fan frenzy.
"Fifty Shades of Grey" has a release date of Aug. 1, leaving producers Michael De Luca and Dana Brunetti scrambling to find a replacement for Hunnam.