The Outlet in Banbridge is set to be sold for around £40million alongside Junction One retail park in Antrim.
The deal for both sites will be completed in the next few weeks, according to press reports.
The sites were marketed together and had an original asking price of £60million.
Banbridge-based Lotus Group are the company believed to be buying the retail parks.
The Outlet park was opened in 2007 at a cost of £70m.
It has a number of big name stores including Marks and Spencers, Gap and Calvin Klein Underwear while bb’s Coffee and Muffins opened their first Northern Ireland store there last month.