The $30million sale is conditional at present, but if it goes through, ownership is expected to transfer on April 30 or shortly afterwards.
Arvida chief executive Jeremy Nicoll said the company would work closely with PSSC to ensure a smooth transition so that care and support continued to be delivered for all residents.
"Strathallan has been a key part of Arvida since 2017 and we look forward to seeing PSSC’s continued commitment to providing a high-quality experience at Strathallan."
Strathallan offers independent living in one, two and three-bedroom villas, semi-independent living in one and two-bedroom serviced apartments and rest-home, hospital and specialised dementia care.
The purchase will add to Presbyterian Support South Canterbury’s portfolio of aged care facilities, which includes The Croft and Margaret Wilson Home in Timaru, and Wallingford Home in Temuka.
The charitable organisation has been operating those facilities for more than 30 years, but its involvement in community service in South Canterbury spans more than 100 years.
PSSC chief executive officer Carolyn Cooper said the purchase of Strathallan would enhance Presbyterian Support’s ability to provide a range of aged care and retirement options in the district.
"We are really excited to be working with the skilled and caring team at Strathallan."
