Subject to resource consent approval, construction work is expected to begin in the second quarter of 2018 with no disruption to existing services.
Director of Acurity Health Group Dr Richard Grenfell said almost 50 per cent of elective surgery in New Zealand was carried out by private surgical hospitals, providing critical support to the public health system and ensuring healthier New Zealanders.
"This investment demonstrates Acurity Health Group's strong and long-term commitment to Royston and to the Hawke's Bay community."
Dr Grenfell said while there had been additions made to the facility, this would be the most significant and bring it up the highest standards.
"The infrastructure around the theatres probably was not adequate so when Evolution Healthcare bought Acurity Health they decided they needed to invest money in Royston to bring it up to a standard, allow growth of patients entering into Royston and also a much higher quality of care."
Patient experience would be enhanced due to the expanded facilities providing better care and staff being able to handle patients more efficiently, he said.
"I feel excited. I'm a medical person, I'm actually a specialist anaesthetist, so I've worked in hospitals all my professional life. To see what is being done in Royston is exciting because the theatres and patient experience will all be top class."
Ms Primrose said a stream of recent investments at Royston had seen top-level endoscopy, sterilisation and surgical equipment all upgraded.
"This significant investment to our facilities represents a major boost to the region's only full service private surgical hospital which has proudly provided an elective surgery option to our community since 1921."
Acurity Health Group had lodged a Resource Consent application with Hastings District Council for the project, and Dr Grenfell said it would be "extraordinarily surprised" if it wasn't approved.