Ustinov's grandfather was a Russian officer in the tsar's army who was exiled because of his religious beliefs. “It is for that reason,” Ustinov later said, “that I am addressing you today in English.” His father was a respected British journalist and his mother an accomplished painter. After attending Westminster School and the London Theatre School, Ustinov made his professional stage debut at age 17, playing an old man in a production of The Wood Demon. The performance was something of a portent of things to come, as Ustinov's acting career has been characterized by numerous roles in which he displayed his talents for vocal mimicry and age affectation. After a few uncredited bit parts in British films, he landed his first major screen role in The Goose Steps Out (1942).

Despite his impressive résumé, acting was merely one of many creative outlets for Ustinov. A playwright of considerable note, equally appreciated in New York City and in London, Ustinov wrote The Love of Four Colonels (performed 1951), Romanoff and Juliet (1956; filmed 1961), Halfway up the Tree (1967), The Unknown Soldier and His Wife (1967), in which he also starred when the play was chosen to open the New London Theatre in 1973, Overheard (1981), and Beethoven's 10th (1983), a comedy in which he himself starred as the great composer. His credits as a motion-picture director include the aforementioned Billy Budd, the screen adaptation of Romanoff and Juliet, and the darkly comic Hammersmith Is Out (1972) with Elizabeth Taylor (Taylor, Elizabeth) and Richard Burton (Burton, Richard). Lady L (1965) with Sophia Loren (Loren, Sophia) and Paul Newman (Newman, Paul) was probably his best-received directorial effort. Ustinov also wrote most of the films he directed, and in 1969 he received an Oscar nomination for his screenplay for Hot Millions.

Whether in print or before a live audience, Ustinov was a skilled storyteller and master of the English language. His best-selling works of prose include the short-story collection Add a Dash of Pity (1959), the novels Krumnagel (1971) and Monsieur Rene (1999), the historical study My Russia (1983), and the autobiographical works Dear Me (1977), Ustinov at Large (1991), and Ustinov Still at Large (1993). A renowned raconteur, Ustinov was acclaimed for his glib and humorous lectures and one-man shows.

Ustinov's efforts as a humanitarian were as visibly effective as his creative output was prodigious. Ambassador at large for UNICEF from 1969 until his death, he received that organization's Medal for Distinguished Service in 1993. He was made Companion of the Order of the British Empire in 1975 and was knighted in 1990.