Staff at more than 160 public hospitals and community health services across the state have notified the union about their plans to strike next week.
They are protesting over what they say is the state government’s failure to provide safe nurse staffing levels.
NSW Nurses and Midwives Association General Secretary Brett Holmes says more branches were expected to join the cause by Wednesday.
The union wants one nurse to four patients in all general medical, surgical and acute inpatient mental health wards.
It’s also calling for one nurse per three children in general children’s wards and one nurse to three patients in emergency departments.