Walton, the son of a choirmaster father and a vocalist mother, studied violin and piano desultorily as a boy and also sang, with somewhat better results, in his father's choir. He taught himself composition, although he received advice from both Ernest Ansermet and Ferruccio Busoni. In 1912 he entered the University of Oxford, where he sang in the choir of Christ Church. He put in the requisite four years of study but failed by one examination (Responsonions) to win a bachelor of music degree. At Oxford he had met the Sitwell (Sitwell, Sir Osbert, 5th Baronet) brothers, Osbert and Sacheverell (Sitwell, Sir Sacheverell, 6th Baronet), by whom he was virtually adopted, and he spent most of the next decade traveling with them or living with them at Chelsea. During this period he composed Façade (1923)—a set of pieces for chamber ensemble, to accompany the Sitwells' sister Edith (Sitwell, Dame Edith) in a recitation of her poetry—as well as Sinfonia Concertante for piano and orchestra (1928; revised 1943) and Portsmouth Point (1926), which established his reputation as an orchestral composer.

Walton was influenced by some of his older contemporaries, notably Edward Elgar, Igor Stravinsky, and Paul Hindemith (Hindemith, Paul). Hindemith was soloist in the first performance of one of Walton's finest works, his Viola Concerto (1929). Walton also composed a number of scores for motion pictures, including Major Barbara (1941), Henry V (1944), Hamlet (1947), and Richard III (1954). His vocal music includes the oratorio Belshazzar's Feast (1931) and the operas Troilus and Cressida (1954) and The Bear (one act; 1967). The composer received a knighthood in 1951.