Regan was born in Romford, Essex, to Irish parents. Before becoming a singer, Regan worked at a number of jobs, including re-touching photographs. Her successful singing career began in 1953, when she made a demo record of "Too Young" and "I'll Walk Alone". The demo came to the attention of Bernard Delfont, and that helped her sign a recording contract with Decca Records. She had a number of Top 40 hits for the label, many of them were cover versions of American hits. Among them were Teresa Brewer's "Ricochet", "Till I Waltz Again with You", and "Jilted", Doris Day's "If I Give My Heart to You" and Jill Corey's "Cleo and Me-O" and "Love Me to Pieces". 　　She became the resident singer on BBC producer Richard Afton's television series Quite Contrary. Afton later replaced Regan with Ruby Murray. She appeared on the Six-Five Special, and was also given her own BBC television series, Be My Guest, which ran for four series. After being knocked out by a descending safety curtain during her first appearance in variety, she developed her act to include impressions of Gracie Fields, Judy Garland and actress Anna Neagle, to whom she bore a facial resemblance. 　　In the late 1950s, she appeared several times at the London Palladium, including the Royal Command Performance and also in the show Stars in Your Eyes. In 1958, she appeared as herself in the film Hello London. 　　On leaving Decca in 1958, she signed with EMI's HMV label, where she had a Top 10 hit with a cover version of the McGuire Sisters' "May You Always". Two years later, she left EMI for Pye Records, and had two minor record successes, ("Happy Anniversary" and "Papa Loves Mama"). 　　In 1957, she married Harry Claff who was the joint general manager and box office manager at the Palladium. In November that year, the Daily Herald reported Regan was to have a baby in February 1958, seven months after the wedding. After receiving "abusive and wounding letters from people who were personally unknown to her", Regan successfully sued the newspaper for libel; her daughter was actually born in April. Claff and Regan divorced in 1963 after he was jailed for five years for fraud. By this time, the hits had completely dried up and she suffered a nervous breakdown. Regan moved to Florida and married Dr. Martin Cowan, a medical doctor. 　　In the United States Regan recorded two singles for Columbia (one of which, "Don't Talk To Me About Love", went on to become a Northern soul classic). In 1984 she slipped in the shower, hit her head on the tiles and suffered a brain haemorrhage. After an emergency operation she was left paralysed and speechless. 　　Her recovery, which entailed much physical and speech therapy, was aided by her miming to her old records. It took many months of treatment before she regained the ability to sing. In 1987, some of those old tracks, together with others by Dickie Valentine, Lita Roza and Jimmy Young, were issued on the double album, Unchained Melodies. In the 1990s, she returned to the UK where, with the help and encouragement of Russ Conway who had been her rehearsal pianist in the early 1950s, she returned to the stage. She recorded for Nectar Records from 1992 to 1996, for whom she recorded a single "You Needed Me" and two albums, The Joan Regan Collection and Remember I Love You.