Born in Montpelier Square in Knightsbridge, London, Joyce Grenfell was the daughter of architect Paul Phipps (1880–1953), the grandson of Charles Paul Phipps and a second cousin of Ruth Draper. Her mother was an American socialite, Nora Langhorne (1889–1955), one of five daughters of Chiswell Langhorne, an American railway millionaire. Nancy Astor, née Nancy Langhorne, was one of her mother’s sisters, and had also married in England. Grenfell often visited her at Astor’s home of Cliveden  and later lived on a cottage on the estate (‘Parr’s’), a mile from the main house, in the early years of her marriage. Joyce Phipps had an upper-class London childhood. She attended the Francis Holland School in Central London, and the Claremont Fan Court School, in Esher, Surrey. She was “finished” in Paris where she attended Mlle Ozanne’s finishing school at the age of seventeen. In 1927, she met Reginald Pascoe Grenfell (1903–1993). They were married two years later at St Margaret’s, Westminster, and remained married for nearly 50 years (until her death). She made her stage debut in 1939 in the Little Revue. In 1942 she wrote what became her signature song, “I’m Going to See You Today.” During World War II, Grenfell toured North Africa, Southern Italy, the Middle East and India with her pianist Viola Tunnard performing for British troops. In 1989, her wartime journals were published under the title The Time of My Life: Entertaining the Troops. Her singing and comedic talents on stage led to offers to appear in film comedies. Although she performed in a number of films, she continued with her musical recording career, producing a number of humorous albums as well as books.

As a writer at the BBC during and just after the war, she collaborated with Stephen Potter in writing the “How” series of 30 satirical programmes from How to Talk to Children to How to Listen. During the 1950s she made her name as a sidekick to such comedy greats as Alastair Sim and Margaret Rutherford in films such as The Happiest Days of Your Life (1950) and the St Trinian’s series. She was also a member of the influential Pilkington Committee on Broadcasting from 1960 to 1962. Her fame reached as far as the USA and she appeared on The Ed Sullivan Show alongside Elvis Presley. Grenfell is now best remembered for her one-woman shows and monologues, in which she invented roles including a harassed nursery teacher (“George – don’t do that”). She gained additional popularity as a result of her frequent appearances on the BBC’s classical music quiz show, Face the Music. Although her humour appeared light and frilly on the surface, there was often a serious point to be made: the song “Three Brothers”, for example, appears to recount the happy, busy life of a spinster in lightweight terms, but it essentially describes her willing slavery to her male siblings and their families. Much of the music for Grenfell’s revues and shows was the result of a collaboration with the composers and pianists Richard Addinsell and William Blezard. From 1954 to 1974, Blezard composed Grenfell’s songs and spoof operettas such as Freda and Eric. They performed on stage and television all over Britain, America and Australia. Although her singing career is best remembered for her self penned humorous songs she did also record standards such as Noël Coward songs ‘If love were all’ and ‘The party’s over now’.

Like her maternal aunt, Lady Astor, Grenfell was a member of the Church of Christ, Scientist, a religious organisation based on Christianity and spiritual healing. She was taken ill in 1973 with an eye infection, which was subsequently diagnosed as cancer although she was not told. The eye was removed and replaced with an artificial one. No one except those close to her were ever advised of this. She kept on performing and appearing on the BBC2 programme Face The Music. In October 1979 she became seriously ill and died just over a month later, on 30 November 1979, just before her golden wedding anniversary. She was cremated at Golders Green Crematorium on 4 December and her ashes placed in section 4-D of the Garden of Remembrance.