Born in Naples, Italy, Leonetti studied at the Cooper Union and the Art Students League in New York in the 1910s. After serving in the United States Army during World War I, he became an American citizen in 1920. He returned to New York and settled into the city's bohemian community—acting in films, studying dance and voice, and opening The Pirate's Den, a themed nightclub in Greenwich Village. While managing the nightclub, he began producing portraits of the artistic crowd, and he eventually supported himself primarily as a photographer of celebrities. He documented the lively world of theater and dance. He continued to paint and exhibit his work. He was a member of the Whitney Studio Club and active in the governance of the Art Students League.
