Born in Pisa, Galli started his career with his home town’s youth side as a midfielder before switching to the role of goalkeeper. He began his professional career with ACF Fiorentina in 1977, where he played for nine Serie A seasons. In 1986–87, he joined fellow league side A.C. Milan, being first-choice for three of his four years, and establishing himself as one of Italy’s best goalkeepers, winning the Serie A title and the Supercoppa Italiana during his first season. He also started in both of the club’s back-to-back European Cup conquests, in 1989 and 1990, also winning consecutive European Supercups in 1989 and 1990, and the Intercontinental Cups in 1989. He also reached the final of the 1989–90 Coppa Italia with Milan. In the 1990 summer, following Milan’s signing of Sebastiano Rossi, 32-year-old Galli left, going on to represent S.S.C. Napoli and appearing in an average of 33 league games during his three-year spell, starting by winning the Italian Supercup, 5–1 against Juventus. In the summer of 1993 he signed for Torino A.C. and in the following season he finished his stint in the top division, at the end of the 1994–95 season, after being named backup goalkeeper behind Luca Bucci at AC Parma, who won the UEFA Cup that season, and reached the Coppa Italia final, also placing third in Serie A. Galli retired in 1996 at the age of 38 after a brief stint with A.S. Lucchese-Libertas of Serie B.