A once-vacant hospital campus in Williamsburg is getting a major transformation, with plans for both a new homeless shelter and hundreds of affordable housing units.

The former Greenpoint Hospital site, unused since the 1980s, is being redeveloped into the 200-bed Barbara Kleinman men’s shelter. The project preserves some of the landmark building’s original architecture, including columns from the old nurses’ residence that will now serve as the building’s dining hall.

“It has been underutilized, vacant and a blight on the community for nearly 50 years now,” said developer Joe Riggs, of Hudson Companies.

When it opens, the shelter will offer dorm-style rooms with air conditioning, increased privacy and wraparound services to support Brooklyn’s most vulnerable residents, including 70 beds reserved for men suffering from mental health challenges.

“You're already talking about people that are hard to engage, living on the streets and not wanting to talk to people,” said Jamie Madden, COO of Project Renewal. “Having the services in-house helps support them where they are.”

Just next door, construction is underway on 350 affordable housing units, set to open within two years.

Rents could be as low as $400 a month, with 104 of the units reserved for families exiting the shelter system, starting at 30% of the Area Median Income.

“Three hundred fifty units — it's going to make a dent in the need for affordable housing in this neighborhood,” said Michael Rochford, director of St. Nicks Alliance.

Rochford adds that the building's first floor will feature a glass terrace to preserve the view of the historic hospital exterior from the nearby park.

The shelter is expected to open this November, marking the first of four phases of what community leaders hope will be a transformative campus for the area.