Move to the United States
After appearing in small roles in British films such as The Best of Enemies (1961), Hot Enough for June (1964) and Where the Spies Are (1965) Harrison left for the United States in 1965, working as a nightclub entertainer at such venues as the Hungry I in San Francisco, and at the Persian Room in New York City. Thanks to his managers Bob Chartoff and Irwin Winkler, who went on to produce the Rocky films, he had a record reach the charts. The track was "A Young Girl", written by Charles Aznavour. In the 1966–67 television season he appeared as Mark Slate in 29 episodes of the NBC series The Girl from U.N.C.L.E. as the costar of Stefanie Powers (April Dancer). A year earlier, Norman Fell originated his Mark Slate character on the original U.N.C.L.E. series, The Man from U.N.C.L.E. in a second-season episode titled "The Galatea Affair". In 1968, Harrison appeared on an episode of To Tell the Truth in which the panel had to figure out which of three women was Harrison's then-wife Sara.
"Young Girl" was included as one of the tracks on Harrison's debut album, Noel Harrison, in 1966. Two years later, he recorded "The Windmills of Your Mind", the theme tune from the film The Thomas Crown Affair, which won the Academy Award for Best Original Song in 1968, and was also a Top 10 hit in the UK Singles Chart. Despite the song winning the 1968 Oscar for best original song, Harrison did not sing it at the ceremony. Instead his place was taken by Jose Feliciano. The change was made because he was working on the film, Take A Girl Like You in England, with Oliver Reed and Hayley Mills. Coincidentally, his father had sung the Oscar-winning song ("Talk to the Animals") only the previous year (1967).
The television series, plus the Top 40 record, landed Harrison a recording contract with Reprise, who released three of his albums, Collage, Santa Monica Pier and The Great Electric Experiment Is Over. Collage reached #135 in the United States Billboard 200 chart. He also toured with the Beach Boys, and Sonny and Cher, appeared on The Ed Sullivan Show, featured on a music program, Hullabaloo and appeared on The Tonight Show Starring Johnny Carson.
In 1968, Harrison played the male lead in The Fantasticks, in touring theatres in the round, including the Cape Cod Melody Tent in Hyannis, Massachusetts. In 1970, he played the male lead role in "Blithe Spirit" at The Cape Playhouse in Dennis, MA and returned in 1983 for the lead male role in "The Housekeeper".