A stretch of road at Ballyduff West in the Kilmeaden area reopened at midnight last night following a serious collision on Sunday afternoon.
The accident involving three cars happened at 3.45.
Four people were taken to University Hospital Waterford.
Its understood those involved were the drivers of the three cars – a female in her 60s, two males in their 20s and 50s and a female passenger.
Gardaí have said their injuries are not life threatening.