Waldhorn studied acting at the Yale School of Drama (graduated 1967) where he notably performed in new works written by Playwright Lillian Hellman in 1966. While at Yale he met fellow student Christie Dickason, daughter of Indiana University academic David Howard Dickason, who became his wife and an active theater Director and Choreographer in London and a later a published Playwright and Novelist. He is known for his work in West End theatre productions and for his collaborations with the Royal Shakespeare Company. In 1972 he toured Australia and New Zealand in Harry Miller's production of Sleuth playing opposite Richard Todd.
Apart from appearing in every episode of The Vicar of Dibley, Waldhorn has also made many television appearances since the 1970s including Softly, Softly, The Sweeney, Space: 1999, The New Avengers, Brideshead Revisited, The Professionals, Minder, Robin of Sherwood, Rumpole of the Bailey, The Bill, Heartbeat, Gallowglass and Lovejoy. He also played Lionel Bainbridge in the first three series of Brush Strokes, and Richard Beamish in the first series of All at No 20.
