Cahill made his competitive debut for Australia at the 2004 OFC Nations Cup. Cahill finished the competition as second-highest scorer in the competition with six goals, and was the top scorer in the final round. Australia went on to win the competition for the fourth time in their history. Having won the competition, Australia were drawn against Uruguay in the World Cup qualification play-off. Cahill played in the game as Australia beat Uruguay after a penalty shoot out to qualify for the World Cup for the first time in over 30 years.