The issue is affecting both the east and westbound carriageways and National Highways have said it is due to works by Yorkshire Water.
The roads agency said on social media: "The A64 both directions around Malton. Delays are being picked up in the area due to some ongoing Yorkshire Water roadworks in place. Please make time for your journey."
Repair works have been ongoing on the road for the past few weeks to replace safety barriers.
The AA's traffic site reports: "Severe delays on A64 both ways between the Hutton turn-off and B1248 York Road (Musley Bank). Congestion to Whitwell on the Hill and also back to the Old Malton Roundabout."
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The issue has forced the Coastliner bus to put a diversion in place.
The bus company tweeted: "Hi Folks, due to heavy traffic on the A64 we will be unable to serve all stops between Welburn & Malton, buses to divert via Coneysthorpe.
"This diversion is in place until further notice."