Fiore made 8 appearances for Italy's Under-21 side, and 3 appearances for the Under-23 side, with which he won the Mediterranean Games in 1997. He made his Italy national football team senior debut during his time with Udinese, under manager Dino Zoff, on 23 February 2000, taking part in a 1–0 victory in an international friendly against Sweden, in Palermo. Fiore's fine form during the 1999–2000 Serie A season soon allowed him to become a permanent and important member of the national side, earning him a place in Dino Zoff's national side for Euro 2000. He had a very successful tournament and scored what many regard as the goal of the tournament in the 2–0 victory over co-hosts Belgium, in Italy's second group match; he also assisted a goal for his creative, offensive midfield teammate Francesco Totti in the quarter-finals of the tournament, a 2–0 win over Romania, which sealed Italy's place in the semi-finals against co-hosts the Netherlands. His fine form continued as he went on to take part in all of Italy's matches throughout the competition, as they reached the final, only to lose to the defending World Champions France on a golden-goal in extra-time.