Shrewsbury Prison, at The Dana, near the town's railway station, announced on social media that it has now bought the remainder of the prison complex.
A spokesman said: "We are pleased to announce that we have exchanged contracts on the rear buildings and land at the former prison site.
"There are some exciting plans for the development of this historic site, which has become one of Shropshire's top tourist destinations."
Shrewsbury Prison is run by Cove Group.
