Green Cross Health plans to buy Peak Primary, which owns 11 medical centres throughout the North Island and Christchurch.
Chair of Green Cross Health Peter Merton said the details of the purchase are confidential for now, but will be released eventually.
The purchase is part of Green Cross' plans to expand its primary healthcare business.
The company represents about 300 pharmacies throughout New Zealand, under the brands of Unichem and Life Pharmacy.
It also offers community health services under the Total Care Health Services brand.
Mr Merton said Peak Primary fits well with the medical centres it already operates under The Doctors brand.