Born in Trieste, at very young age Gentilomo moved to Rome, where at 21 years old he entered the cinema industry, working as a script survivor and an assistant director. Active between 1933 and 1937 as a film editor, in 1939 he debuted as a director with Il Carnevale di Venezia.In 1945 his film O sole mio got critical acclaim, but later his career was mainly devoted to genre films, and failed to achieve significant critical interest.Dissatisfied with cinema, in the mid-1960s Gentilomo decided to abandon films and to fulfill his passion for painting