Julio de Diego was born May 9, 1900 in Madrid, Spain. At the age of 15 he was an apprentice to a set designer at an opera company, and his first exhibition was held in a gambling casino when he was only 17. Due to his family's opposition to his art career, de Diego moved to Paris in 1922. During this time he studied ballet and acting. In 1924, he came to the United States and settled in New York City, where he stayed until 1931. During this time, de Diego traveled to Tampa and designed sets and costumes for "The Wild Cat" at Centro Asturiano. He also worked for the WPA, painting "street scenes, landscapes, and 'some very terrible murals.' " 

Between 1931-1942 de Diego lived in Chicago and exhibited at the Art Institute of Chicago. Other exhibition locations included the Chicago Renaissance Society, the New York World's Fair, the Whitney Museum, the Carnegie Institute, the Metropolitan Museum of Art, Associated American Artists, Bonstell Gallery, and Nierendorf Gallery.

De Diego married Gypsy Rose Lee on March 19, 1948 and they divorced on August 8, 1955.  He played the part of Miguel in the 1958 film "The Buchaneer" He moved to Florida and taught at the New College in Sarasota, Florida, where he was also well known for his jewelry. He died in Sarasota on August 22, 1979.