High Street, Narberth, is to be closed for the next four Sundays to enable water main refurbishment work to be carried out in the carriageway.
The main A478 road will be shut - starting this Sunday (October 12) - from its junction with Market Square, north to its junction with Moorfield Road (B4314).
An alternative route for northbound traffic will be via St. James Street, which will be made two-way under temporary traffic light control.
"Pedestrian access will be maintained for the duration of the closure, together with limited vehicular access to affected properties along High Street," said a spokesman for Pembrokeshire County Council.