Adi Birrell's Irish team will aim to qualify for the 2007 World Cup
Ireland will be the venue for the 2005 ICC Trophy with the hosts hoping to be among the five qualifiers for the 2007 World Cup in the Caribbean.
Matches will take place on both sides of the Irish border.
The Irish Cricket Union hopes the first phase of the competition will be played in Northern Ireland with the concluding stages in Dublin.
"The organisational skills of the Irish Cricket Union are well known within the ICC," said ICC President Ehsan Mani.
ICC chief executive Malcolm Speed joined Mr Mani in Belfast for Thursday's announcement,
The agreement was signed in front of government officials as well as executives from the Northern Ireland Events Company and the Sports Council for Northern Ireland.
Irish Cricket Union officials are pleased they have convinced the ICC that it will be viable to play the competition on both sides of the border.
The final format for the competition in Ireland will be decided at an ICC meeting at Lords on 29 June.
Irish Cricket Union chairman Joe Doherty said the confirmation of the competition was a major boost for the sport in Ireland.
"The fact the tournament will be played north and south will spread the message of cricket throughout the island," said Mr Doherty.
"The union is grateful to the ICC for breaking with the tradition of a single centre. All we need now is for Ireland to qualify for the World Cup finals."