Director Scott Stewart announced on his Twitter page that the two actors have joined Priest.
However, we still do not have details on their respective roles in the upcoming comic book adaptation.
The film will star Paul Bettany in the role of a warrior priest, who turns against the church to track down a band of killer vampires who have kidnapped his niece. The film takes place in a world ravaged by the aftermath of centuries of war between humans and vampires.
Priest is set to hit theatres on August 13, 2010. The film will also star Cam Gigandet, Mädchen Amick, Maggie Q, Karl Urban, Stephen Moyer and Lily Collins.
In the meantime, we can see Christopher Plummer in The Imaginarium of Doctor Parnassus on Christmas Day, and Brad Dourif in Bad Lieutenant: Port of Call New Orleans, which has not been given an official opening date.