Following his eight successful years in Peñarol in his native Uruguayan league, Schiaffino started to play in the Italian Serie A in September 1954. He played 171 games with AC Milan and scored 60 goals, and participated in the 1958 European Cup Final, which Milan lost to Real Madrid 2–3 (aet). He was among the crucial offensive players in a Milan team that was dominated by foreign stars such as Nils Liedholm and Gunnar Nordahl. Schiaffino won three national championships with Milan, the victories being in 1955, 1957 and 1959. Schiaffino scored a world leading 145 goals for Milan but left in 1960 to join Roma, where he played out his career during two moderately successful seasons, in which Roma finished fifth in the standings.