On Thursday afternoon, the Industrial Relations Commission sensationally blocked the action, planned from 7am to 7pm.
However, more than 90 per cent of Australian Paramedics Association [APA] members voted on Thursday night to defy the orders.
The Hunter workers joined colleagues across the state in "partial strike action" to fight for fair pay, amid concern about increased workloads, burnout and the rising cost of living.
During Friday's industrial action, paramedics limited responses to non-emergencies and didn't do routine transfers. They continued to do "sirens and lights" emergency cases.
APA NSW president Brett Simpson said "this strike symbolises our unyielding quest for justice".
"This fight is about our paramedics' welfare and the quality of healthcare for everyone in NSW," Mr Simpson said.
The decision to defy the orders meant paramedics faced "potential legal repercussions and a substantial fine of up to $20,000 per day".
"As the lowest paid in the country, our paramedics not only suffer financially but also experience a draining of skilled professionals to other states."
He said paramedics were working with "exhaustion and a sense of continuous betrayal since the election of the Minns government".
"The issues run deep."
"There is money set aside in the budget for public sector wage increases, yet every time we ask about it we get crickets," he said.
Opposition health spokesman Matt Kean said the Labor government had promised a pay increase for paramedics ahead of the election and now the "chickens are coming home to roost".
"Paramedics deserve to be paid what their premier promised and Chris Minns promised huge pay increases in line with inflation."
The Health Services Union [HSU], which also represents paramedics, is seeking an immediate 20 per cent pay-boost to align them with Queensland.
About 1900 of its paramedics had signed a pledge to "boycott their professional registration".
"Paramedics are sick of being treated like ambulance drivers," an HSU spokesperson said.
The boycott meant that in a month, paramedics who had not signed their registration would be banned from the "higher order clinical work they now do".
"It will have a significant impact if it's not sorted by early January."
NSW Health Minister Ryan Park has acknowledged paramedics' pay no longer matches the skills required, but was concerned about budget challenges.