In 1924, Zanini enrolled in the night class of drawing and arts at the São Paulo School of Arts and Crafts, which he completed in 1926.
Mario Zanini began a painting course at the Escola de Belas de São Paulo (or School of Arts of São Paulo), in São Paulo, at the age of 13. In 1924, he enrolled in the night class of drawing and arts at the São Paulo School of Arts and Crafts, which he completed in 1926. Two years later, he studied with the painter Georg Elpons.
Mario Zanini worked as a lyricist at Companhia Antarctica Paulista between 1922 and 1924. Then he worked in the decoration office of Francisco Rebolo between 1933 and 1938. His first solo exhibition took place in 1944 at the gallery of Livraria Brasiliense in São Paulo, Brazil.
In 1950 Zanini travelled to Italy. He then taught engraving at the Paulista Association of Fine Arts and at the Carlos de Campos School in 1958. Since 1968 he taught at the Faculty of Fine Arts of São Paulo.
Zanini died on August 16, 1971 in Sao Paulo, Brazil.
Mario Zanini was a member of the Grupo Santa Helena.