The closure is between Dudley Road and Chestnut Hill Road/Route 53, police said.
The road will be closed for repairs for about eight to 16 hours, police said.
The closure is near the intersection with Route 7.
Police are warning motorists that there could be extensive delays in the area. The closure is for about a mile, and is near the border with Westport, Weston and Norwalk.
Click here to follow Daily Voice Wilton and receive free news updates.