The proposed new store is anticipated to be occupied by national retailer B&M.
The new unit would add just under 2,000sqm of additional retail space.
As well as a garden centre on site, a B&M store would offer a range of goods including DIY, toys and games and homeware.
The store will also increase local employment opportunities, creating around 30 new jobs within Alnwick.
The proposed unit would be an extension to the already successful phase 1 development at the Northumberland Estates owned retail park and complements the existing retail line up which includes M&S, Turnbulls Northumbrian Foodhall and a Starbucks drive thru.
The additional outlet is designed to increase spending within the Alnwick area, benefitting the local economy and reducing the need to travel further afield encouraging more sustainable shopping patterns.
Shona Ferguson of Northumberland Estates says: “This would be a great addition to the area, providing more retail choice for residents in Alnwick and the surrounding areas.
"The development would have a positive impact on the local economy, creating jobs for local people and encouraging increased spending in the town as a whole, another sign of ever-growing confidence in the town.”
Planning permission for the retail park, on the southern outskirts of the town, was granted in June 2018.
It will be the first unit to be built since M&S, which opened in January 2020.
It will eventually have a total of 37,405 sq.ft. of retail floorspace, plus onsite parking for some 200 vehicles, once full phase development is complete.