Dealership manager Adrienne Ensor said the country's dealers were assessed each month on all aspects of their new and used car sales and after-sales service to determine which consistently scored the highest.
"You've got to perform consistently every month," Mrs Ensor said.
The Dunedin business won the award in 1991 and 2006, and it was a finalist last year.
Only one other dealership had won the award three times before.
Ms Ensor attributed the win to customer loyalty, experienced staff and the stability provided by the 114-year-old Cooke Howlison name.
"There is stability in it. Customers like to know the people who deal with them will be around for the life of the vehicle."
The Toyota dealership employed 50 staff, and 110 were employed by the entire Cooke Howlison group.
