Born in Derbyshire, England, Bates earned a scholarship to the Royal Academy of Dramatic Art in London, where he studied before leaving to join the Royal Air Force. In 1956, he debuted on stage in the West End, starring in Look Back in Anger, a role which made him a star. Four years later, he appeared in The Entertainer, his first film role. He soon starred in Whistle Down the Wind, and in the Bernard Malamud film The Fixer, which gave him an Academy Award nomination for Best Actor.

He was married to the actress, Victoria Ward, from 1970 until her death of a suspected heart attack (following a wasting disease) in 1992; they had twin sons born in 1971, the actor, Benedick Bates, and Tristan Bates (also an actor), who died of an asthma attack in Tokyo in 1990 at the age of 19.

Bates starred in such international hit films as Georgy Girl, Far From the Madding Crowd, Zorba the Greek, The Go-Between, An Unmarried Woman and Women in Love, but he consciously decided to concentrate on a few well-defined roles, rather than to take everything that came his way. On television, his parts ranged from classic roles such as The Mayor of Casterbridge (1978) to Guy Burgess in An Englishman Abroad (1983) to the storyteller in the 2000 version of the Arabian Nights.

On stage, Bates had a particular association with the plays of Simon Gray, appearing in Butley, Otherwise Engaged, Stage Struck, Melon, Life Support and Simply Disconnected, as well as the film of Butley and Gray's TV series Unnatural Pursuits.

Bates was made a Commander of the British Empire (CBE) in 1996, and was knighted in 2003.

His companion at the end of his life was actress Joanna Pettet; he died of pancreatic cancer in 2003 at the age of 69.