Greatwich began his international career with the Philippines in 2004, making his debut against Myanmar in the Tiger Cup. He was unable to play in 2005 in the SEA Games due to his Hartwick Hawks making the NCAA Tournament in the United States, but played the following year in Bacolod when they hosted the qualifiers for the Asean Championships. It was here that Greatwich scored his first international goal against Laos in the side's 1–2 defeat. He then scored in the 7–0 win over East Timor and played in wins against Cambodia and Brunei to see them qualify for the finals in Thailand. There they lost to Malaysia and Thailand before drawing with Myanmar in their final game.