Walton was born in Oldham in Lancashire and after singing as a choirboy at Christ Church Cathedral in Oxford, entered Christ Church College, Oxford. He was taught compostion by Hugh Allen at first, but from 16 was largely self-taught.
Walton was friends with the literary Sitwell family: Osbert Sitwell, Sacheverell Sitwell and Edith Sitwell. It was setting some of Edith's poems as Façade (1922, for reciter and chamber group) which first brought Walton to the attention of the musical world. He had originally been introduced to the Sitwells by Siegfried Sassoon, who had taken an interest in his progress since their first meeting at Oxford (when Walton was only 17 and Sassoon already an established poet).
His other works include two symphonies (1935 and 1960), concertos for violin (written for Jascha Heifetz), viola (written for Lionel Tertis but premiered and championed by Paul Hindemith), and cello (for Gregor Piatigorsky), the oratorio Belshazzar's Feast (1931), and the operas Troilus and Cressida and The Bear (based on the Anton Chekhov play). He also wrote film music, including that for Laurence Olivier's film Henry V.
Walton was knighted in 1951 and received the Order of Merit in 1968. He died in 1983 in Ischia in Italy, where he had made his home.