The Kuaotunu River Bridge on State Highway 25 on the Coromandel Peninsula will be closed for the next five weeks from today as repair work is carried out.
The bridge was damaged in heavy rain earlier in September.
The New Zealand Transport Agency said an assessment of the damage was made and contractors would work as hard as they could to repair it as quickly as possible.
Its Waikato System Manager, Karen Boyt, said the agency understood the effects the closure could cause for local people and those travelling in the area.
"We understand the frustration this may cause for those who live in or travel to the area often, however, our contractors are working as hard as they can to repair the damage as quickly and efficiently as possible," she said.
NZTA hoped to have the bridge open again by Labour Weekend, but it would be weather dependent.
"We will keep the community updated, and we ask motorists travelling to the area to check our Journey Planner, or call 0800 44 44 49 before leaving for the most up-to-date information about the repairs," said Ms Boyt.
Residents south of Blackjack Road will be able to access Kuaotunu from Whitianga and those living west of the bridge will only have vehicle access from the Coromandel side.
Pedestrians will be able to cross the river via a separate, existing walk bridge.