Chamberlain co-founded a Los Angeles–based theater group
Company of Angels, and began appearing on television in guest roles in the early 1960s. In 1961, he gained widespread fame as the young intern Dr. James Kildare in the
NBC/MGM television series of the same name, co-starring with
Raymond Massey.
Dr. Kildare ended in 1966, after which Chamberlain began performing on the theater circuit. In 1966, he was cast opposite
Mary Tyler Moore in the ill-fated Broadway musical ''
Breakfast at Tiffany's, co-starring Priscilla Lopez, which, after an out-of-town tryout period, closed after only four previews. Decades later, he returned to Broadway in revivals of My Fair Lady and The Sound of Music''. At the end of the 1960s, Chamberlain spent a period of time in England, where he played in repertory theater and in the BBC's
Portrait of a Lady (1968), and reprised the role for television in 1970 for the
Hallmark Hall of Fame. A recording of the presentation was released by
RCA Red Seal Records and was nominated for a
Grammy Award. including
Centennial (1978–79), and reprised the role of Aramis in the last of the trilogy
The Return of the Musketeers (1989). From the 1990s to his death in 2025, Chamberlain appeared mainly in television films, on stage, and as a guest star on such series as
The Drew Carey Show and
Will & Grace. as well as two episodes of season 4 of
Chuck where he played a villain known only as The Belgian. Chamberlain also appeared in several episodes of
Brothers & Sisters, playing an old friend and love-interest of
Saul's. He also appeared in the independent film
We Are the Hartmans in 2011. In 2012, Chamberlain appeared on stage in the
Pasadena Playhouse as Dr. Sloper in the play
The Heiress. In 2017, Chamberlain appeared in
Twin Peaks: The Return as Bill Kennedy. == Personal life and death ==