The former Gravesend and North Kent Hospital site has been bought for £2.3 million.
NHS Property Services (NHSPS) has sold the Bath Street site, which is also known as M-Block and has been empty since 2006, to Peker GYO.
It comes with outline planning approval for up to 80 homes and community facilities and was offered to other public bodies before being placed on the open market.
Funds from the sale will be reinvested in the NHS.
David Thurgar, senior transaction manager at NHSPS, said: “This sale is a great example of how we help the NHS by using our expertise to unlock potential and achieve maximum value for surplus sites.
“As well as generating funds for reinvestment, this site could help meet the Government’s targets for releasing public sector land for much-needed new homes.”
Gravesham Community Hospital, on an adjacent site, is unaffected by the sale and continues to operate as normal.
Hasan Peker, chairman of Peker, said: “We are extremely excited about coming to Gravesend.
"Our business model is about developing homes in town centres which are well connected and create a real sense of place.
"We have a great track record of spending a lot of time and effort in refining our proposals to ensure we are delivering the highest quality development.
“This will be our first project in Gravesend and we are currently in discussions about another prominent town centre site.”
Dalian Gill, a spokesman for Peker and MD of Gravesend-based planning firm Barron Edwards, said: “We often see initial interest from developers and investors in major development sites in Gravesend, however investment seems to be skipping the town and heading straight over to Medway.
"More investment into local development will provide homes, jobs and a boost for local businesses through the economic output of these developments.
“We are looking forward to working on this project. The M Block site has an extant outline permission but there’s much more work to do on the detailed design."
A detailed planning application will now be prepared and submitted to Gravesham council during the summer with construction expected to start in the first half of 2019.