Originally Peter Ellstrom Deuel, he was born in Rochester, New York, and arrived in Hollywood in 1963. His first major television appearance was in a series called Gidget (1965), and then in a sitcom, Love on a Rooftop. Having changed the spelling of his name, he finally made the big time when he was cast as the outlaw Hannibal Heyes in 1970. Alias Smith and Jones was at the height of its popularity when, just after Christmas, 1971, Duel shot himself, apparently in a suicidal frame of mind after suffering from chronic depression. His role in the series was taken over by Roger Davis, but with limited success, and the series was cancelled in 1973.
His younger brother, Geoffrey Deuel, is also an actor.