During the 2003–04 season, Carvalho earned his first cap for the Portugal national team on 11 October 2003 in a 5–3 friendly match win over Albania. He established himself as a key member of the national team starting XI during the UEFA Euro 2004 championship on home soil, after replacing captain Fernando Couto in the heart of Portugal's defence following the team's defeat against Greece in the opening group game. In the tournament, he was nominated for the UEFA Euro Team of the Tournament along with his compatriots Maniche, Luís Figo and Cristiano Ronaldo. Carvalho formed a strong partnership with Jorge Andrade in the Portuguese defence as his country reached the final, though they lost 1–0 to Greece in a stunning upset. Carvalho started in all of Portugal's six games in the tournament, including an epic game against England, where the defender was named Carlsberg Man of the Match, and Portugal emerged victorious 6–5 on penalties. BBC Sport football expert Alan Hansen said that Carvalho was, along with Sol Campbell, the best defender at Euro 2004.