Firefighters were called to the farmlands after a tractor was spotted alight in a field.
Crew members from Dartford Fire Station attended the blaze in Daltons Road, Crockenhill, near Swanley soon after 10pm.
They were alerted by a driver who spotted the burning vehicle.
One fire engine was deployed and four firefighters used a hose jet to douse the flames.
It took them around 30 minutes to clear the incident, as one crew member remarked: "It was quite a huge fire as the tractor was quite big."
The incident has been reported to the police and is being treated as suspicious.