The facility originally supposed to cost in the region of 450 million euro.
The cost of the New Children's Hospital is now estimated to be 2.24 billion euro.
The previously approved budget was 1.73 billion euro.
Health Minister Stephen Donnelly gave an update to Cabinet this morning.
Ministers approved an additional half a billion euro to the cost of the National Children's Hospital.
The main new hospital building will deliver 300 individual inpatient beds, 60 critical care beds, 20 Child and Adolescent Mental Health Services beds, and 93 day-beds.
The facility originally supposed to cost in the region of 980 million euro.
There have been multiple cost overruns since construction began, and it's set to be the most expensive hospital in the world.