Born in Montpelier Square in Knightsbridge, London, Joyce 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 middle class London childhood. Among her friends was Virginia Graham, with whom she kept up a lifelong correspondence. 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 until her death nearly 50 years later. They were unable to have children of their own.
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 the Second World War, 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, the latter being the first programme broadcast on the BBC Third Programme, on 29 September 1946. 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 US 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.
Grenfell 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.
In February 1980, a memorial service was held at Westminster Abbey, the first time such an honour had been granted to a comedian. Only Les Dawson and Ronnie Barker have been similarly honoured since.
Grenfell was created an Officer of the Order of the British Empire (OBE) in 1946. It was confirmed after her death that she would have been made a Dame Commander (DBE) in the 1980 New Year Honours List.
In 1998, the Royal Mail memorialised Grenfell with her image on a postage stamp as part of a series of stamps celebrating Heroes of Comedy.
Her widower, Reggie Grenfell, died in Kensington and Chelsea, London, in 1993, aged 89.
In 2002, her friend and author Janie Hampton published the book Joyce Grenfell. In a 2005 poll to find the Comedians' Comedian, she was voted amongst the top 50 comedy acts ever by fellow comedians and comedy insiders.
Maureen Lipman has often toured with the one-woman show Re: Joyce!, which she co-wrote with James Roose-Evans. In it she recreates some of Grenfell's best-known sketches. Lipman also presented the radio programme Choice Grenfell, compiled from Grenfell's writings. Roose-Evans also edited Darling Ma, a 1997 collection of Grenfell's letters to her mother.Ensa Tour, Baghdad; Setif, Algeria (1944)
Sigh No More, Piccadilly Theatre, London (1945)
Tuppence Coloured at the Globe Theatre, London (1947)
The Little Revue (1949)
Penny Plain at St Martin's Theatre, London (1951–52)
Joyce Grenfell Requests the Pleasure at the Fortune and St Martin's, London (1954)
Joyce Grenfell in an evening of monologues and songs at the Haymarket, London (1962)
Grenfell, Joyce (1976). Joyce Grenfell Requests the Pleasure. London: Macmillan. ISBN 0-333-19428-4.
Grenfell, Joyce (1977). George, Don't Do That. London: Macmillan. ISBN 0-333-22080-3.
Grenfell, Joyce (1979). In Pleasant Places. London: Macmillan. ISBN 0-333-27288-9.
Grenfell, Joyce (1988). Edited by James Roose-Evans, ed. Darling Ma. London: Hodder & Stoughton. ISBN 0-340-42368-4. CS1 maint: Extra text: editors list (link) Letters to her Mother, 1932–1944
Grenfell, Joyce; Compiled and introduced by Janie Hampton (2000). Hats Off: Poems and drawings. London: John Murray. ISBN 0-7195-6152-3.