The actor, who plays Liam McPoyle on It's Always Sunny in Philadelphia, will portray Josh Speed, the personal assistant and friend to Abraham Lincoln. He joins a cast that already includes Benjamin Walker, Anthony Mackie, Dominic Cooper, and Mary Elizabeth Winstead.
Timur Bekmambetov will direct from a script by Seth Grahame-Smith, who adapted his own novel of the same name. The story centers on Lincoln, who goes on a quest to slay vampires after discovering that his mother was actually murdered by a vampire years ago.
Production will start next month.