Ansermet studied at Lausanne and from 1906 to 1910 taught mathematics there. Later he studied composition under the Swiss-born composer Ernest Bloch and conducted under two outstanding figures, Felix Mottl and Arthur Nikisch. About 1914 he met Stravinsky and in 1915 he became conductor of Diaghilev's Ballets Russes. In 1918 he formed the renowned Orchestre de la Suisse Romande, of which he remained the conductor until his retirement in 1967. He frequently toured Europe with the orchestra and made many recordings with it. Ansermet was a notable exponent and interpreter of the works of Stravinsky, Ravel, Debussy, Roussel, and other contemporary composers. Late in life he turned against 12-tone music (e.g., in his book The Fundamentals of Music in the Human Consciousness, 1961), although he continued to espouse other contemporary music.

His own works include a symphonic poem, settings of poems by Baudelaire, and the orchestration of Debussy's Épigraphes antiques.