The supermarket giant says staff and customers will be updated on the exact closure date for the store at the top of Brook Street after two decades in the town.
Cardiff-based commercial estate agents, Fletcher Morgan, has placed the property on its catalogue.
A new tenant would have to pay £115,643 a year to let the building, which has a 11,519 square feet footprint.
The Welshpool store was revealed as one of those Sainsbury's was closing in March.
The retail giant announced two years ago that it wanted to close 15 stores.
A spokesman said: "We have updated colleagues on the difficult decision to close our Welshpool store in July and we are doing everything we can to find alternative roles within Sainsbury’s for those affected.
“Customers can continue to shop with us at our Oswestry and Shrewsbury Superstores.”
A large Tesco store opened in the Welsh market town in 2011 and since then an Aldi has also opened close to the Tesco.
Earlier this year Welshpool lost its WH Smith, stationers store and the bank, HSBC has announced it will leave the town in the Autumn.