Layoff notices go out Wednesday to workers at the hospital and its related facilities.
Management tells Newsday it needs to trim staff to help close a projected $50 million budget gap.
The budget shortfall is blamed on rising pension costs, reduced Medicaid payments and higher operating expenses.
The layoffs mostly affect lower-wage employees represented by the Civil Service Employees Association. They are effective immediately.
CSEA president Jerry Laricchiuta warns patient care will be impacted.
NUMC also plans to cut $10 million in contract costs; eliminate $6 million in overtime and negotiate $4 million in givebacks from doctors.
The plan still leaves the hospital with a $5.5 million budget hole.