According to Deadline, Walk The Line star Phoenix is the first choice to play Henry Sturgess, a man who saves the teenage Lincoln from vampires and teaches him how to slay the bloodsuckers.
Benjamin Walker was last week named as the star for the big budget project.
Timur Bekmambetov will direct Vampire Hunter, while Tim Burton is producing.
Phoenix last appeared in Casey Affleck's film I'm Still Here, which documented the actor's retirement from Hollywood. Phoenix and Affleck both maintained that the movie was genuine during production, only to confirm it was a hoax shortly after release last year.