Temple Street Children's Hospital says it is currently off-call for ambulances, due to an isolated fault in sub-area of the hospital's electrical system.
The problem is still affecting one area in the emergency department, since it began at 9.30am.
It is affecting telephone lines and lighting.
Parents are being encouraged to attend their local GP if at all possible, however if the matter is urgent, the Temple Street emergency department is still operational.
As a safety measure, all scheduled surgeries, which included 14 day cases and three in-patient cases, were postponed this morning.
Four elective MRI scans also had to be postponed this morning.
The hospital said that emergency surgeries will go ahead this afternoon.
All other current in-patients in the hospital are stable and being cared for within existing resources.
Temple Street said that the temporary power failure continues to demonstrate the need for a new children's hospital.