More than 5600 cars were registered in January, 23% more than in December, and 10.8% more than in the same month a year ago.
Used car registrations, which are generally for imported used cars, were 3.5% higher than a year ago, while commercial registrations were 19.1% higher.
Toyota remained the most popular make, followed by Holden and Ford.
The Motor Industry Association says the jump in the number of new cars on the road is good news not only for car companies, but also the wider economy.
Chief executive Perry Kerr says about three-quarters of new cars are purchased for business fleets, so the increase suggests economic confidence is improving.
He says the motor industry is predicted to continue to grow this year, but at a more modest rate. Last year's growth was 14.8%.