Construction was originally due to begin before the end of March but was postponed when lockdown was ordered.
Additional planning was then required following the Covid-19 outbreak to ensure the work could be carried out safely with social distancing and other measures in place.
The £30m scheme will improve a 2.2km stretch of the carriageway in north Wales by removing direct accesses off the A55 as well as removing eight gaps in the central reservation which currently allow slow agricultural vehicles to cross the A55.
It will also deliver more flood protection for the A55, though the construction of an improved drainage system.
Alun Griffiths director Martyn Evans said: “We are delighted that work is now due to commence to deliver these vital safety improvements on the A55 – providing safer journeys for road users and improved access for those living alongside it.
“As a result of coronavirus, we have embedded additional safety measures that exceed current government guidance, to protect our workforce and the local communities in which we will be working.”