Repairs to safeguard the future of Skeeby Bridge on the A6108 are set to start next week.
The work, which will include rebuilding the parapet walls, is due start on Monday and continue until early October.
Traffic lights will be in place on the bridge throughout the work.
The work is going ahead despite concerns from conservation bodies.
The Society for the Protection of Ancient Buildings (SPAB) and The Council for British Archaeology (CBA) both objected to changes to the historic low-lying classical style bridge which features a number of arches, saying the alterations could ruin the structure.
But North Yorkshire County Council planners approved the work on the bridge, which is listed as a nationally important structure, after hearing the authority had been left with large bills after some of its bridges collapsed in recent years.
Members were told the grade II listed bridge had become an eyesore bridge due to the impact of traffic, weathering and previously poor techniques of repair.
Due to the objections the final decision was passed to the Secretary of State for Local Communities.