A former Republic of Ireland under-21 international, Delap won 11 caps for the national team between 1998 and 2004. He was not included in the Irish squad for the 2002 FIFA World Cup, where the nation reached the final sixteen of the tournament. His international career was marked by a number of withdrawals, the last of which was with a twisted knee on 25 April 2004 before a midweek friendly with Poland.