Harrison's film debut was in The Great Game (1930), and other notable early films include The Citadel (1938), Night Train to Munich (1940), Major Barbara (1941), Blithe Spirit (1945), Anna and the King of Siam (1946), The Ghost and Mrs. Muir (1947), and The Foxes of Harrow (1947). He was best known for his portrayal of Professor Henry Higgins with Audrey Hepburn in the 1964 film version of My Fair Lady, based on the Broadway production of the same name (which itself was based on George Bernard Shaw's play Pygmalion), for which Harrison won a Best Actor Oscar. He also starred in 1967's Doctor Dolittle. Harrison was not by general terms a singer; thus, the music was generally written to allow for long periods of recitative, generally identified as "speaking to the music." Nevertheless, "Talk to the Animals", which Harrison performed in Doctor Dolittle, won the Academy Award for Best Original Song in 1967. His son, Noel, coincidentally sang the 1968 Oscar winner, "The Windmills of Your Mind".
Although excelling in comedy (Noël Coward described him thus: "the best light comedy actor in the world—except for me."), he attracted favourable notices in dramatic roles such as his portrayal of Julius Caesar in Cleopatra (1963) and as Pope Julius II in The Agony and the Ecstasy (1965), opposite Charlton Heston as Michelangelo. He also acted in a Hindi movie Shalimar alongside Indian Bollywood star Dharmendra.
Harrison was married six times. In 1942 he divorced his first wife, Colette Thomas, and married actress Lilli Palmer the next year; the two later appeared together in numerous plays and films, including The Fourposter.
In 1947, while married to Palmer, Harrison began an affair with actress Carole Landis. Landis committed suicide in 1948 after spending the night with Harrison. Harrison's involvement in the scandal surrounding Landis' death briefly damaged his career and his contract with Fox was ended by mutual consent.
Harrison and Lilli Palmer divorced in 1957. That same year, Harrison married actress Kay Kendall. Kendall died of leukemia in 1959. He was subsequently married to Welsh-born Rachel Roberts from 1962 to 1971 (Roberts committed suicide in 1980). Harrison then married Elizabeth Rees-Williams and, finally, Mercia Tinker, who would become his widow in 1990.
Chronology of Harrison's six marriages
Colette Thomas (1934–1942 - divorced), (one son, the actor/singer Noel Harrison)
Lilli Palmer (1943–1957 - divorced), (one son, the novelist/playwright Carey Harrison)
Kay Kendall (1957–1959 - her death)
Rachel Roberts (1962–1971 - divorced)
Elizabeth Harris (1971–1975 - divorced), (three stepsons, Damian Harris, Jared Harris, and Jamie Harris)
Mercia Tinker (1978–1990 - his death)
Granddaughters: Cathryn, Harriott, Chloe, Chiara, Rosie, Faith
Grandsons: Will, Simon, Sam
Having retired from films in the late 1970s, Harrison continued to act on Broadway until the end ofhis life, despite suffering from glaucoma, painful teeth, and a failing memory. In 1989 he appeared on Broadway in The Circle by W. Somerset Maugham, opposite Glynis Johns and Stewart Granger, when he fell ill. He died of pancreatic cancer at his home in Manhattan on 2 June 1990 at the age of 82.
Harrison's second autobiography, A Damned Serious Business: My Life in Comedy (ISBN 0553073419), was published posthumously in 1991.