Wilmot made his film debut in the 1990 film The Field and went on to appear in Michael Collins (with Liam Neeson), The Devil's Own, and The General (with Jon Voight). Slightly more mainstream appearances include The Laws of Attraction (with Pierce Brosnan and Julianne Moore) and the 2004 film King Arthur.
Wilmot also appeared in the 2005 Academy Award-winning short film The Six Shooter, as a grieving father. On television, he starred as Dr. Ed Costello on the RTE series The Clinic. His stage credits include the title role in The Lieutenant of Irishmore, first in England in 2002, in Dublin in 2003, and finally on Broadway in 2006 (netting a Tony Award nomination for Best Actor).