It is likely to open to customers in April next year.
The branch will buy and sell vehicles, and offer on-site finance and insurance.
There will be a wide selection of used cars, including ex-lease and Japanese imports, a weekly auction and retail sales.
Turners Auto Retail chief executive Greg Hedgepeth said the dealership would enable it to buy more local cars.
“Our nearby branches in Palmerston North and New Plymouth have had great success, and this new branch in Whanganui will allow us to better serve the region,” Hedgepeth said.
“It’s something that we’ve been considering for a while now and we’re very happy to be able to expand the network into Whanganui – it definitely meets our criteria and it’s great to be able to invest in an important area of New Zealand.”
Hedgepeth said there was “still plenty of water to go under the bridge” with the development but the Turners team were working hard to open on the targeted date.