The child was struck by the vehicle in Montrose Avenue at the junction with Burnt Oak Broadway, Edgware, at about 19:15 BST.
Police and the ambulance service attended the scene, but he was pronounced dead in hospital.
The driver of the car stopped and police said he was helping with their investigation. No arrests have been made.
The boy's next of kin have been informed.
A four-year-old boy died when he was hit by a car in north-west London.