He was born in Oxford, England, and educated at the Dragon School, Gresham's School and Merton College, Oxford. His father was Hastings George Fitzhardinge Berkeley, a captain in the Royal Navy and illegitimate son of George Lennox Rawdon Berkeley, 7th Earl of Berkeley (1827–1888).
In 1927, he went to Paris to study music with Nadia Boulanger, and there he became acquainted with Francis Poulenc, Igor Stravinsky, Darius Milhaud, Arthur Honegger and Albert Roussel. Berkeley also studied with Maurice Ravel, often cited as a key influence in Berkeley's technical development as a composer. The French influence would continue to be felt in his music.
In 1936 he met Benjamin Britten, another old boy of Gresham's School, at the ISCM Festival in Barcelona. He enjoyed a long association with Britten and collaborated on a number of works; these included Montjuïc, and Variations on an Elizabethan Theme (the latter also with four other composers).
He wrote several piano works for the pianist Colin Horsley, who commissioned the Horn Trio and some piano pieces, and gave the first performances and/or made the premier recordings of a number of his works, including his third Piano Concerto (1958).
He was Professor of Composition at London’s Royal Academy of Music from 1946 to 1968, and his pupils there included Richard Rodney Bennett, David Bedford and John Tavener. 1954 saw the premiere of his first opera Nelson at Sadler’s Wells. He was knighted in 1974 and from 1977–83 was President of the Cheltenham Festival. In later years, his adoption of serialism marked a darker and more brooding style.
- Nelson, (1951)
- A Dinner Engagement, Op. 45 (1954)
- Ruth, Op. 50 (1955–6)
- Serenade, for string orchestra (1938–9)
- Symphony No. 1 (1936–40)
- Divertimento (1943)
- Piano Concerto in B-flat major, Op. 29 (1947–8)
- Concerto for Two Pianos and Orchestra, Op. 30 (1948)
- Symphony No. 2 (1958, revised 1976)
- Symphony No. 3, in one movement (1968–9)
- Sinfonia Concertante, for oboe and chamber orchestra (1972–3)
- Voices of the Night, Op. 86 (1973)
- Guitar Concerto, Op. 88
- Symphony No. 4 (1977–8)
- A Festival Anthem, Op. 21, No. 2 (1945)
- Crux fidelis, Op. 43, No. 1 (1955)
- Look up, sweet babe, Op. 43, No. 2 (1955)
- Missa Brevis, Op. 57 (1960)
- Mass for five voices, Op. 64 (1964)
- Three Latin Motets, Op. 83, No. 1 (1972)
- The Lord is my shepherd, Op. 91, No. 1 (1975)
- Magnificat and Nunc dimittis, Op. 99 (1980)
Solo Vocal 
- Four Poems of St Teresa of Ávila, Op. 27, for contralto and string orchestra (1947)
- Three Greek Songs, Op. 38 (1953)
- Five Poems by W. H. Auden, Op. 53
- String Quartet No. 1, Op. 6
- String Quartet No. 2, Op. 15
- String Quartet No. 3, Op. 76
- Sonata in D minor for viola and piano, Op. 22 (1945)
- Trio for horn, violin and piano, Op. 44 (1952)
- Sextet for clarinet, horn and string quartet, Op. 47 (1954)
- Duo for cello and piano
- Sonatine for flute and piano
- Three Pieces, Op. 2 (1935)
- Piano Sonata in A major, Op. 20 (1941–5)
- Six Preludes, Op. 23 (1945)
- Three Mazurkas, Op. 31 No. 1 (1939–49)
- Quatre pièces pour la guitare (1928)
- Sonatina, Op. 52, No. 1 (1957)
- Theme and Variations, Op. 77 (1970)
Selected recordings 
- A Dinner Engagement – Chandos CHAN10219
- Missa Brevis – Naxos 8.557277
- Serenade for Strings – Chandos CHAN 9981
- Lennox Berkeley's homepage at Chester Music
- The Lennox Berkeley Society
- Performance of Duo for cello and piano (video)
- Peter Dickinson The Music of Lennox Berkeley - Page 77 2003 "Colin Horsley remembered Berkeley's time at the BBC because he was reputed to have kept manuscript paper under his desk and was obviously longing to get more time to compose.27 Since it was there that he met his wife it is no wonder .."
- Musical leader 1958 Page 21 "Lennox Berkeley launched his Third Piano Concerto with Colin Horsley, for whom the work was written, at the Royal Philharmonic Society's Festival Hall series recently"
- Review Sextet May 2008, quote: Berkeley wrote his three movement Sextet for Clarinet, Horn and String Quartet, Op. 47 in 1954 for the Melos Ensemble.