Jane Asher was born on 5 April 1946 in London, the middle of three children born to Richard and Margaret Asher. Her father was a consultant in blood and mental diseases at the Central Middlesex Hospital, as well as being a broadcaster and the author of notable medical articles. Her mother was a professor at the Guildhall School of Music and Drama. Her elder brother is record producer Peter Asher of Peter and Gordon fame; her younger sister Clare Asher is a radio actress and school inspector.

Jane launched her acting career when she was just six years old, with the role of Nina in the film Crash of Silence (1952). By the time she was fifteen, she had appeared in eight films, made nine television appearances, over 100 radio appearances, and was in five plays. Her notable early films included The Quatermass Xperiment (1955), The Greengage Summer (1961), The Prince and the Pauper (1962), and Alfie (1966).

She met Paul McCartney for the first time on 18 April 1963 at the Royal Albert Hall in London. The concert was broadcast live by the BBC on the programme Swinging Sound. Asher broke off the engagement in summer 1968, and has consistently refused to publicly discuss that part of her life. Asher met illustrator Gerald Scarfe in 1971 and they married in 1981 and have three children.

In 1990, she founded her own cake shop, Jane Asher Party Cakes, which has become a renowned establishment in London. She has authored several baking books, sharing her expertise with baking enthusiasts worldwide. With Britain more obsessed than ever with baking, Jane Asher brought together a selection of recipes from the nation’s favourite television chefs for Best Bakes Ever on BBC Two (2015–2016), giving baking fans a chance to experience classic dishes from James Martin, Mary Berry, Paul Hollywood, the Hairy Bikers, Raymond Blanc, and Nigella Lawson, among others.