He was registered at birth as Mozart Guarnieri, but when he began a musical career, he decided his first name was too pretentious and subject to puns. Thus he adopted his mother's maiden name Camargo as a middle name, and thenceforth signed himself M. Camargo Guarnieri. In 1948, he legally changed his name to Mozart Camargo Guarnieri, but continued to sign only the initial of his first name. One of his brothers was named Rossine (a Portuguese misspelling of Rossini) Guarnieri, another one Verdi Guarnieri.
He studied piano and composition at the São Paulo Conservatório, and subsequently worked with Charles Koechlin in Paris. Some of his compositions received important prizes in the United States in the 1940s, giving Guarnieri the opportunity of conducting them in New York, Boston, Los Angeles and Chicago. A distinguished figure of the Brazilian national school, he served in several capacities; conductor of the São Paulo Orchestra, member of the Academia Brasileira de Música, and Director of the São Paulo Conservatório, where he taught composition and orchestral conducting. In 1936 he was the first conductor of the Coral Paulistano choir. His œuvre comprises symphonies, concertos, cantatas, two operas, chamber music, many piano pieces, and over fifty canções. He is universally recognised as the most important Brazilian composer after Heitor Villa-Lobos. Shortly before his death in 1993, he was awarded the Gabriela Mistral Prize by the Organization of American States as the greatest contemporary composer of the Americas.
Silva, Flávio. Camargo Guarnieri: o tempo e a música. Rio de Janeiro: Ministério da Cultura, FUNARTE; São Paulo, SP: Imprensa Official SP, 2001 ISBN 85-7507-009-6.
Verhaalen, Marion. Camargo Guarnieri, Brazilian Composer: A Study of his Creative Life and Works, with a preface by José Maria Neves. With CD recording. Bloomington: Indiana University Press, 2005. ISBN 0-253-34475-1.