The steel bridge will be blast cleaned and repainted to protect it from the salty tidal water.
Work will start on Monday 1 June on a 13-week project to repaint, repair and protect Boston's Town Bridge.
Whilst work takes place, one lane of the bridge will remain open for traffic. The southbound bus lane will be closed, with services diverted.
Pedestrians will still be able to cross the bridge while work takes place with social distancing measures in place to help keep them safe.
Cllr Richard Davies, executive member for highways at Lincolnshire County Council, said:
"At high tide, parts of the steel structure of the bridge can be submerged under the water line, so it's imperative that we keep the bridge well maintained to protect it from the elements.
"The specialist protective paint we use on the bridge needs to be applied at a certain temperature and humidity to work effectively, so we need to carry out this work during the summer months.
"Thankfully, the coronavirus pandemic has had very little impact on the project, as the nature of the work and the extra measures we have put in place mean that the crew will be able to maintain at least 2m distance between them."