Part of the A55, also known as the North Wales Expressway, will be closed from 9pm on Saturday January 12 until 3am on Sunday January 13.
Work by SP Energy Networks to complete an upgrade to a main overhead power cable between Valley and Caergeiliog means a section of the major route will be shut for six hours.
The new 132 thousand volt wood pole overhead line is part of a £13m investment programme to reinforce electrical infrastructure across Anglesey.
A diversion route will be in place during the closure and is approximately 1.7m (2.8km) long through Caergeiliog on the old A5.
We fully appreciate that the A55 is an essential route for the area and have worked closely with the Local Authority and its highways department to ensure this work is timed during one of the quietest periods following Christmas and avoiding key ferry times. We will endeavour to minimise disruption where possible but would advise anyone planning to travel within the night time closure to allow additional journey for the diversion.