 Amadei represented the Italian national team on 13 occasions between 1949 and 1953, scoring 7 goals; he made his international debut on 27 March 1949, in a 3–1 friendly away win over Spain.The following year, he participated in the 1950 FIFA World Cup with Italy, where he made one appearance during the tournament, in a 2–0 win over Paraguay.Following his retirement in 1956, Amadei worked as a coach for Napoli, the club with which he retired.