A native of Paraná, Argentina, Castrogiovanni made his international debut for the Italian national team on June 8, 2002, during the tour against the All Blacks, and since, has become a regular in the national side. He played every game of Italy's 2004 Six Nations campaign and was a reliable member of their forward pack, being selected man of the match in the victory against Scotland. One of his most famous moments came in 2004, when, during the summer tour against Japan, he scored a hat-trick - a rarity for a prop forward. He led the national team for the game against Scotland during the 2012 Six Nations Championship, which Italy won 13-6, leading him to Tweet "Only unbeaten 6 Nations Captain".