The Wrestler actor had signed up to play Conan's father in the new movie alongside former Baywatch star Jason Momoa, who will tackle the role made famous by Arnold Schwarzenegger in the 1982 original.
But Rourke has now dropped out of the production, and will be replaced by Hellboy star Ron Perlman, according to Moviehole.net.
Perlman was previously involved with the animated Conan TV series, voicing the lead role.
Conan The Barbarian is slated for a 2011 release.