William McNamara pursued artistic formation through studies at Salisbury School, followed by Columbia University and training at the Lee Strasberg Institute in New York. He began performing in film and television in the late 1980s, transitioning from early screen appearances to recurring roles on television series. His career includes portrayals of historical figures in television movies, regular participation in a Showtime series, and roles in episodic television law dramas. Beyond acting, he engages in animal-rights activism: he began by rescuing domestic and farm animals, later producing documentaries on the exotic animal industry for the Nat Geo Wild network.