NSW Health questioned the media's reporting that union action would take place on Thursday.
However 60 to 100 health staff from Bowral, Campbelltown, Camden and Liverpool took part in a one-hour strike at Campbelltown Hospital.
They were among 22,000 NSW Health Services Union (HSU) members that took part in planned statewide action to call for additional 250 security guards at NSW hospitals.
In a statement to the media, NSW Health denied union action would take place.
"NSW Health would like to reassure the public that media reports suggesting some 22,000 workers will stop work on Thursday are not accurate," a spokesperson said.
HSU NSW secretary Gerard Hayes said he was "extremely proud" of the union members that walked off the job.
"These members have sacrificed pay to stand up both for their own safety and also that of the general community," Mr Hayes said.
"It is extremely disheartening to see the Ministry of Health engage in a campaign of deliberate misinformation and intimidation.
"Yesterday, the Ministry propagated the false claim that today's strike was off... HR managers were taking photographs of workers who went on strike.
"The Ministry's energy would be far better spent improving safety at hospitals and extracting funding from treasury to employ an extra 250 security officers."
Wollondilly MP Nathaniel Smith said he had discussed the strikes with Health Minister Brad Hazzard.
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"The Health Minister has acknowledged there are continuing concerns about security issues in our hospitals, which is why a review has been implemented and headed by a former Labor Police and Health Minister Peter Anderson," Mr Smith said.
"Mr Anderson is due to submit a final report for the Government's consideration at the end of 2019."
A NSW Health spokesperson said the department was "committed to addressing security issues with its workforce".
Mr Hayes said Thursday's strike was the beginning of a campaign that would now intensify.
"The level of violence against hospital workers is sickening," he said.
"There are more than 40 assaults in NSW hospitals each month. In the last three years, our members have been shot, stabbed, punched, bitten and spat upon. Enough is enough."
Minister Hazzard's office was contacted for comment.