Galli played for 16 seasons (305 games, 111 goals) in the Italian Serie A for U.S. Città di Palermo, A.S. Roma, A.C. Milan, Udinese Calcio, Genoa C.F.C.

He was one of manager Giuseppe "Gipo" Viani's favourite players, and he coached while at both Palermo and Roma, before joining him at Milan in 1956, in exchange for an ageing Gunnar Nordahl.

In his five seasons with Milan, Galli won two Serie A titles, and scored 47 goals, including five in a 6–1 home win over Lazio on 13 April 1958 at the San Siro.

[2][3] At international level, Galli earned 13 caps and scored 5 goals for the Italy national team between 1953 and 1959, and participated in the 1954 FIFA World Cup.

[3][5] Throughout his career he was nicknamed "Carletto," as well as "Testina d'oro" (golden head), and "Esile giunco" (skinny reed), due to his playing style, aerial prowess, and physical build.