NSW Labor health spokesman Ryan Park said the coalition must listen to the workers' demands.
"Men and women deserve to be able to go to work and come home without being assaulted," Mr Park said on Thursday at a rally outside the NSW health ministry offices in Sydney.
The Shooters, Fishers and Farmers Party also backed the widespread industrial action.
"It is appalling that it has come to this," Shooters MP Mark Banasiak said in a statement.
"(Health Minister Brad Hazzard) has failed to listen to health care workers in their attempts to bring attention to the very unsafe working environment they deal with daily."
Mr Hazzard himself argues the issue of security in hospitals is "more complex" with drug use to blame for increased levels of violence.
"There are major issues in regard to the incredibly good work our staff do but the incredibly poor circumstances they find themselves in," he told parliament on Thursday.
The minister said the coalition had added more frontline staff to the state's health system than any other NSW government.
HSU NSW secretary Gerard Hayes claims some 40 hospital workers are assaulted every month and Thursday's strike action is just the "starting point".
"There is no way that can be condoned as reasonable or allowed to happen," Mr Hayes told AAP.
He called on the NSW government to commit $50 million for a proactive security team at hospitals including staff trained in mental health, drug and alcohol abuse.
The union has previously called for at least 250 additional security staff to be employed with extra powers.
Spinal surgeon Michael Wong was stabbed 14 times by a mentally ill patient at Western Hospital in Footscray in 2014.
"I see the significance of more and improved hospital security to protect staff who are experiencing more violence related to drugs, the opioid epidemic and mental health crisis," Dr Wong said in a statement.
The NSW Department of Health on Wednesday said an agreement had been reached with the HSU in the Industrial Relations Commission to avert the action and if the union complied then a trial of new security measures would proceed at one Local Health district site.
However, despite the action going ahead the department said it remained committed to a trial of "additional security measures at Gosford and Wyong Hospitals" in "good faith".
Rolling strikes took place at several hospitals across the state including Royal Prince Alfred, Royal North Shore, Westmead Children's, Wollongong, Tamworth, Wagga and Dubbo.
The action involved paramedics - who didn't charge patients for treatment or transport - security staff, allied health professionals as well as administration and catering workers.
Doctors and nurses did not strike but they support Thursday's action.
The NSW Nurses and Midwives' Association says current security measures aren't enough of a deterrent and increased staff-to-patient ratios would help reduce violent attacks.