According to York Regional Police the boy grabbed the steering wheel when his mother ducked into a store in a Markham strip mall.
A few seconds later the boy was driving around the parking lot — with his three-year-old brother in the back seat.
Police said the 12-year-old managed to do a lap of the lot and then pulled the car back into its parking spot.
There were no injuries.
Police say they have spoken to the mother about leaving her keys in the ignition.