In 1906 Oppi abandoned the commercial training for which he had been sent from Vicenza to Vienna and attended a number of Gustav Klimt’s classes. He also studied anatomical drawing, before traveling through Germany and the Balkans. The resulting Symbolist works were exhibited at the Ca’ Pesaro, Venice, in 1910. The following year he moved to Paris, where he studied the works of the Italian Old Masters at the Musée du Louvre and met Severini and Modigliani. During World War I Oppi was wounded, captured, and imprisoned near Linz. On returning to Paris, he exhibited classical paintings at the Salon des Indépendants in 1921. In Milan he joined the Sette Pittori del Novecento but betrayed the group by showing independently at the Venice Biennale of 1924. The disconcerting Ingresque purity of such subsequent works encouraged comparisons with the paintings of German Neue Sachlichkeit artists. In 1928–1932 Oppi painted frescoes of the Life of Saint Francis in the chapel of S. Francesco in the chiesa del Santo, Padua, which anticipated much of the mural art of the 1930s. In 1930 he had a show of his early works at the Galleria Il Milione, Milan, and two years later returned to Vicenza, where for the rest of his career he painted nudes and landscapes.