Kent Fire and Rescue Service was called to reports of a tipper truck alight on the M20 between Junction 9 for Ashford and Junction 8 for Hollingbourne, Maidstone just after midday today.
Two fire engines attended and crews wearing breathing apparatus used hose reel jets to extinguish the flames.
No casualties were reported.
The vehicle involved was towing a trailer carrying a number of lambs, which were removed to safety.
Once the fire was out, crews helped to put the animals back into the trailer. The carriageway was closed while firefighters worked at the scene but has since been re-opened.
Officers from the Highways Agency and Kent Police also attended.