[1][2] Gary Raymond was born in Brixton, London, the younger of twins and the youngest of three brothers, to theatrical parents, both of whom were variety artistes.

He soon followed up with his role as Cliff Lewis in Tony Richardson's film adaptation of John Osborne's Look Back in Anger (1958), opposite Richard Burton and Mary Ure.

Subsequent notable films included: Suddenly, Last Summer (1959), in which he appeared with Katharine Hepburn, Mercedes McCambridge and Elizabeth Taylor; The Millionairess (1960), where Raymond played Sophia Loren's character's husband; El Cid (1961), an epic film in which he played opposite Charlton Heston and Loren; The Playboy of the Western World (1962), which he starred in; Jason and the Argonauts (1963), a fantasy film; and The Greatest Story Ever Told (1965), where he portrayed the apostle Simon bar Jonah, who became Saint Peter.

Notable productions include She Loves Me, Treasure Island, Irma La Douce, The Sound of Music, Grand Hotel, The Complaisant Lover, As You Like It, Hamlet, The Crucifer of Blood, Twelfth Night, Full Circle, Look After Lulu!, Dick Turpin, Lysistrata, Frost at Midnight, The Numbered, Electra, Castle in Sweden, The World of Susie Wong, Gentlemen Prefer Blondes, A Midsummer Night's Dream, Troilus and Cressida, The Jungle Book, Peer Gynt, The Trackers of Oxyrhynchus, The Good Person of Sichuan, My Children My Africa, The Beaux Stratagem, Bent, Sunday in the Park with George, The Wind in the Willows and Follies, as well as dozens of others.

He is also well known for his role as Sergeant Jack Moffitt in the late-1960s American television show, The Rat Patrol (1966–68), which ran for two seasons.