He made his international for the Italy senior side debut under manager Dino Zoff on 16 December 1998, in a friendly match in Rome against the FIFA World-Stars, commemorating the first century since the founding of the Italian Football Federation. He was subsequently called up by Zoff for the 22-man Italian squad that took part at Euro 2000, making three appearances throughout the tournament. His first international goal came against France in the Euro 2000 final, although Italy later conceded an equaliser in the final minute of stoppage time, and were defeated in extra-time from a golden goal. Delvecchio travelled to Korea with the 23-man Italian 2002 World Cup squad, but did not play during the tournament under manager Giovanni Trapattoni. After the World Cup, he scored a goal in a 2–0 friendly win over Northern Ireland, and on 18 February 2004, he made his final appearance for Italy against the Czech Republic, missing out on Trapattoni's Euro 2004 squad. Delvecchio scored 3 goals in 14 starts for the Italy senior team, scoring 4 goals in 22 total appearances for Italy between 1998 and 2004.