The route to Whangārei in the south, however, is still blocked by a massive slip at Helena Bay Hill, which is expected to take weeks to clear.
Much of the North Island was hit by severe storms this week, that brought heavy rain, flooding and landslides.
The Ngaiotonga Bridge itself was not damaged in Sunday’s flood, but a section of the road approach was washed away.
Repairs were delayed because a multitude of slips stopped contractors reaching the site with materials and machinery.
Road access from the northern side was restored on Friday.
Forty truckloads of rock and gravel were used to fill the gaping hole.
For two consecutive hours, between 3am and 5am on Sunday, January 18, as much rain fell on nearby Punaruku each hour as most places in Northland get in the entire month of January.