After retiring from football, Fabbri began a coaching career with Mantova in 1957, in Serie D, the team with which he had retired as a player. During his four years with the club, he took the club to Serie A during the 1961–62 season, winning the 1957–58 Serie D and the 1958–59 Serie C titles. In 1962, he was awarded the "Seminatore d'Oro" award for best coach, and he was subsequently appointed the head coach of the Italian national side.