Sculcoates Bridge will be closed from Monday 1 July to Sunday 21 July for essential repair works.
The bridge in Chapman Street will be closed for three weeks so engineers can carry out a full inspection into the condition of the structure.
The diversion route will be via North Bridge.
Councillor Anita Harrison, portfolio holder for highways, said: “We planned the works to begin on the completion of the upgrade works by Northern Gas Networks in Bankside.
“These are essential works that the authority needs to undertake. We apologise in advance for any disruption this may cause to motorists, cyclists and pedestrians.”