National Highways say the road is closed between Raunds and the A14 junction at Thrapston and problems could continue well into the afternoon.
A spokesman added: "The A14 roundabout is blocked due to an overturned lorry. This is affecting road users joining the A14 from the A45 northbound. Please allow extra time for your journey."
Northamptonshire Police are dealing with the incident alongside other emergency services. A statement issued at just before 11.30am said: "Recovery work is expected to take at least two hours so motorists are advised to avoid the area."