[3] Healy's television credits include voices for the Supermarionation series Captain Scarlet and the Mysterons, Joe 90 and The Secret Service, as well as parts in UFO, The Troubleshooters, Randall and Hopkirk (Deceased), Strange Report, Dickens of London, Space Precinct, and Dallas.

[4][5] He also starred as Dr. Watson opposite Ian Richardson's Sherlock Holmes in the 1983 TV film of The Sign of Four.

[6] His big screen credits include The Double Man (1967), Only When I Larf (1968), Assignment K (1968), Isadora (1968), Patton (1970), Lust for a Vampire (1971), Madame Sin (1972), Embassy (1972), Endless Night (1972), Twilight's Last Gleaming (1977), Winterspelt (1979), Supergirl (1984), and Haunted Honeymoon (1986).

[7] In 1983, Healy received the Laurence Olivier Award for Best Supporting Actor for his role in Guys and Dolls during the 1982 theatre season.

In late 1980s he played the character of Buddy Plummer in the original London run of the Stephen Sondheim musical Follies at the Shaftesbury Theatre.