Benedict was born in Silver City, New Mexico, the son of Alma Marie (née Loring), a journalist, and Mitchell M. Benedict, a doctor. He grew up in Massachusetts. As a young man, he suffered from acromegaly, a pituitary disorder that affects the extremities and face, which accounted for his slightly oversized jaw and large nose. Benedict was best known for his role as Harry Bentley on the television show The Jeffersons. He played this role from 1975 when the show began until 1981, and then returned in 1983 and remained until the end of the show in 1985. His character was a well-mannered Englishman who lived in the apartment next door to George and Louise Jefferson. He worked at the United Nations as a translator and was a bachelor. He was liked by all of the characters on the show except George Jefferson, who found him annoying, but they became more friendly as the show progressed. Harry was also known for telling boring, pointless stories about his past, particularly about his childhood and relatives in England. Benedict also played the recurring character The Number Painter on the long-running children’s PBS show, Sesame Street. In the movie The Goodbye Girl (1977) starring Richard Dreyfuss and Marsha Mason, Benedict played the stage director of a production of Richard III in which Richard III was to be portrayed in the play as a stereotypical gay man. He was the patiently-eccentric butler in Dr. Necessiter’s Gothic-castle apartment in The Man With Two Brains (1983). When Dr. Hfuhruhurr (Steve Martin) complains loudly that he just learned his wife is a slut, Benedict responds, “Yah, I’ve heard this.” He was in a short scene in the mockumentary This Is Spinal Tap (1984), playing Tucker Smitty Brown, the awkward desk clerk who checks in the band. Called a “twisted old fruit” by the band’s manager Ian, he replies, “I’m just as God made me, sir.” In 1988 he played ‘Fairchild’, Dudley Moore’s butler in the movie Arthur 2: On the Rocks, the sequel to the hit 1981 film Arthur. That same year in the film Cocktail he would play a condescending business college professor to Tom Cruise’s main character. In the 1990 film The Freshman, he would again play a condescending professor, this time an NYU film school professor of Matthew Broderick’s main character. He also made an appearance as the incorrectly assumed title character in the 1996 film Waiting for Guffman, another mockumentary involving many of the same writers and actors as This Is Spinal Tap.

Benedict also played the role of a slave trader in Dino De Laurentiis’ Mandingo opposite James Mason and Perry King in 1975. Perhaps his best known movie role was of the Reverend Lindquist in Sydney Pollack’s 1972 film Jeremiah Johnson starring Robert Redford. He also appeared on one episode of Seinfeld as a magazine editor with The New Yorker who was questioned by Elaine about a cartoon in the magazine. He also played a small role in the 1974 film The Front Page as Plunkett, the emissary of the governor. In addition to his varied film and television roles, Benedict was an accomplished theater actor as well, having appeared on Broadway multiple times, notably in Eugene O’Neill’s two-character play Hughie in 1996 (performing with Al Pacino) at Circle in the Square, and more recently in The Music Man in 2000–2001. He appeared Off-Broadway in 1986 in Terrence McNally’s It’s Only a Play.  In 2007, Benedict performed as “Hirst” in Harold Pinter’s No Man’s Land at the American Repertory Theater in Cambridge, Massachusetts. As a director, Benedict directed Frank D. Gilroy’s Any Given Day on Broadway. Off-Broadway, he directed the original production of Terrence McNally’s Frankie and Johnny in the Claire de Lune, and Kathy Najimy and Mo Gaffney’s The Kathy and Mo Show, which won an Obie Award. On December 1, 2008, Benedict was found dead of unknown causes at his home in Martha’s Vineyard, Massachusetts. He was 70 years old. He was awarded a posthumous Elliot Norton Award by the Boston Theater Critics Association in 2009.