Pears studied at the Royal College of Music on an opera scholarship and later with Elena Gerhardt (1883-1961). In 1934 he joined the BBC Singers and toured in the USA with them, becoming a member of the Glyndebourne chorus in 1938.
In 1939 he returned to America to give a number of recitals with Benjamin Britten, with whom he formed a lifelong partnership. Returning to Britain in 1943, Pears joined the Sadler's Wells Opera Company, where he created the title role in Britten's Peter Grimes in 1945.
In the following years Pears sang the leading tenor roles in Britten's operas, including The Rape of Lucretia (1946), Albert Herring (1947), Billy Budd (1951), Gloriana (1953), The Turn of the Screw (1954), A Midsummer Night's Dream (which he co-adapted with Britten) (1960), the dramatic church parable Curlew River (1964), Owen Wingrave (1970), and Death in Venice (1973). He was also renowned for his role as the Evangelist in Bach's St Matthew Passion and for his interpretation of Elizabethan lute songs in partnership with Julian Bream. With Britten he founded and organized the Aldeburgh Festival (1948) and the Britten-Pears School for advanced studies in music.