The nurses union has copped a $350,000 fine for organising a strike during which thousands of West Australian health workers fought for better pay and conditions.

About 3000 nurses and midwives walked off the job at hospitals across the state on November 25 last year after the Australian Nursing Federation ignored a lawful direction from the WA Industrial Relations Commission to call off the action.

That triggered a hearing last month before the full bench of the commission into the union's noncompliance with the senior commissioner's orders banning work stoppages, being absent from duty, walking off the job and closing hospital beds.

The commission on Friday handed down its written judgement, in which it labelled the union's correspondence before the strike "staggering", "belligerent noncompliance" and "dripping with contempt".

"In breach of the no-strike order, at least 1758 members of the ANF employed in the public health system took industrial action by walking off the job or failing to report for duty," Chief Commissioner Stephen Kenner wrote.

"The industrial action included various rallies throughout the state including at Parliament House and Dumas House in Perth, and in Albany, Broome, Bunbury, Geraldton, and Karratha."

Following a negotiation during the hearing, the commission fined the union the agreed amount of $350,000.

"I consider the agreed penalty to be a just and appropriate outcome," Mr Kenner said.

"It reflects the serious nature of the conduct of the ANF as a whole, which conduct occurred over a considerable period of time."

The union's state secretary, Janet Reah, also agreed to pay a $10,000 penalty personally, abide by the WA Industrial Relations Act, and comply with the commission's future orders.

"The registrar submitted that by reason of Ms Reah's conduct, in deliberately and publicly flouting the summons to attend the compulsory conference before the senior commissioner on 25 November 2022, the maximum penalty payable by Ms Reah was appropriate," the commissioner wrote in the judgement.

In a statement, the union said the commission's decision and the fines were the start of a new chapter in the continued push for a fair pay deal for nurses.

Since last year, the ANF has been negotiating for a five per cent pay rise and a tangible timeline for enforceable nurse-to-patient ratios, Ms Reah said.

"Regardless of this fine, ANF members remain resolute in their pursuit of a better wage outcome and their commitment has never been stronger," she said.

"Fining the ANF does not do anything to fix the current problem at hand - WA still needs to offer better incentives to retain the existing workforce and entice both international and interstate nurses to WA."