Dozens of striking staff at Sydney's Northern Beaches Hospital are demanding a one-off 15 per cent salary increase, 30 per cent night-shift penalties, improved leave entitlements and mandated nurse to patient ratios.
The strike will go on until early Tuesday.
The 488-bed hospital, which opened in 2018 to replace two smaller public hospitals, is one of 38 Australian hospitals run by Canadian-controlled Healthscope, owned by a multi-national private investment fund.
The controversial public-private partnership was set up under the former coalition state government.
The NSW Nurses and Midwives' Association is urging the "second-largest private operator to put patients and staff before profits and implement safe working conditions ... so they can provide quality patient care."
But Healthscope says it has been negotiating with the union in good faith and is "disappointed" with the industrial action.
"We've made what we consider to be a market leading wage offer of 13.55 per cent over 3 years in NSW with improved conditions," a spokesperson told AAP on Monday.
"As always, our priority is to provide our patients with the best possible care. We are working with doctors and staff to manage this work stoppage with minimal impact on our patients and employees."
The union says life-preserving care and minimum staffing levels will be maintained throughout the stop-work action.
The mass walk-out comes weeks after a parliamentary inquiry was established after the death of two-year-old toddler Joe Massa.
He and his parents waited three hours in the emergency department at the hospital in September 2024.
His heart attack - caused by significant fluid loss - followed repeated failures by hospital staff to conduct basic observations or respond to the concerns of his mother.
Federal and state politicians, such as independents Sophie Scamps and Michael Regan, have previously raised the inadequate staffing levels at the hospital as a major contributor to burnout and less than satisfactory patient care.
