John Jeremy Lloyd was born in Danbury, Essex to a mother who had been a Dancer, and a petroleum Engineer father who served as an officer in the Royal Engineers at the beginning of World War II. As a child he was sent to live with his grandmother in Manchester and rarely saw his parents, who he claimed had seen him as a failure. His father withdrew him from a private preparatory school in 1943.

Lloyd's first marriage in 1955 to model Dawn Bailey lasted seven years. After their marriage ended, Lloyd was briefly married to Actress Joanna Lumley during 1970, but that union ended with a no-fault divorce ("dissolved") after a few months. In 1992 he married Actress Collette Northrop. In August 2014, Lloyd married Elizabeth "Lizzy" Moberly (b. 1960) a former events manager at Barclays Capital.

Lloyd began his career as a Writer in 1958 before making his film debut two years later in 1960 in School for Scoundrels, and appeared in numerous film and television comedies during the 1960s and 1970s. Notably, he was a regular performer on Rowan & Martin's Laugh-In during the 1969–70 television season. Back in England, after the season had been completed, he met Actress Joanna Lumley. A decision had to be made as to whether he would return to the U.S. America for the start of the new season or remain in the UK and marry Lumley. He never returned to the United States.

In A Hard Day's Night (1964) Lloyd is uncredited as a tall man dancing at the disco with Beatles Drummer Ringo Starr. In Help! (1965), he is a restaurant patron, also uncredited. In 1969, he filmed a scene with Peter Sellers for The Magic Christian, which co-starred Ringo Starr. Lloyd can be seen in a boardroom meeting offering marketing slogans for a really big car, and suggests "the gang's all here back seat." In 1967 he played the eccentric chimney sweep, Berthram Fortesque Wynthrope-Smythe, aka Bert Smith, in The Avengers episode, From Venus With Love.

Lloyd's first major success as a comedy Writer was with Are You Being Served? in 1972, on which he worked with David Croft. He and Croft subsequently produced 'Allo 'Allo!, which was equally popular in the UK, and a spinoff of Are You Being Served?, Grace & Favour, which aired in 1992. Lloyd wrote the poem/lyrics for the popular Captain Beaky album and books in 1980.

In 1993 Lloyd published his autobiography, entitled with a phrase from 'Allo 'Allo!, called Listen Very Carefully – I Shall Say This Only Once (BBC Books: ISBN 0563362030).

Lloyd was the subject of what was considered an urban legend, that he had been invited to a dinner party at the home of Sharon Tate on the night that she was murdered by followers of Charles Manson. However the story was verified as true when the octogenarian was interviewed by Emma Freud on the BBC Radio 4 programme, Loose Ends, on 10 December 2011.

Lloyd was appointed an Officer of the Order of the British Empire (OBE) in the 2013 New Year Honours for services to British comedy.

Lloyd died on 23 December 2014, aged 84, after being admitted to a London hospital with pneumonia. He was survived by his wife Elizabeth.