The man is believed to helped the woman who died in the car.
He jumped into the car to try to free her, but then the vehicle caught fire.
The man then began shouting at bystanders for help, and they were able to find a fire extinguisher.
The man, who does not want to be identified, extinguished the fire and stayed with the woman in the car along with another man who was administering first aid.
However, their brave efforts were unable to save the woman.
Northland road policing Senior Sergeant Ian Row said the man's actions were commendable.
"This is exactly what I would expect good people to do. He acted with intelligence and urgency and although he could not have saved her life, he preserved her body."
Row said other road users were not as helpful, including about 12 members of the motorcycle event "To the Top". Not only did they not stop to help at the crash, but they also ignored a police officer trying to stop them.
"They simply carried on their merry way," Row said.
Northland's road toll for the year so far is now 31, compared with 27 for the whole of 2016.