He appeared as a regular in several short lived series on ABC and Showtime, and landed guest spots on TV shows such as The X-Files and NYPD Blue among others, before playing two distinctly different characters on the HBO series Deadwood: Jack McCall in 2004 and Francis Wolcott in 2005 (Dillahunt returned in an uncredited role as a townsman in the 2019 Deadwood movie).
After spending years appearing in theatrical productions on and off Broadway, Dillahunt began pursuing television and film roles.