NSW's acute mental health system has been in turmoil in recent months after 62 public psychiatrists quit and scores more have switched into higher-paid contract roles.
Others are threatening to follow colleagues out the door.
Their union says successive governments have failed to address a retention crisis and calls to lift pay and conditions to rates paid by neighbouring states.
The public hospital doctors were already stretched thin before January's mass resignation, with more than 140 of 433 public psychiatrist positions vacant.
But the state government has baulked at a one-off 25 per cent pay bump, pointing to the already high salaries compared to other health workers and the high cost to the budget.
The stand-off is due to be arbitrated over five days at the Industrial Relations Commission, beginning on Monday.
The doctors union said there was a need for urgent action before more psychiatrists leave.
"Many more psychiatrists are on the edge of walking away. The current situation is just not sustainable," union president Nicholas Spooner said.
"My psychiatrist colleagues are burnt out, and there is no light at the end of the tunnel.
"They are dedicated to providing the best care for their patients, but they cannot provide safe care under these conditions."
Mental Health Minister Rose Jackson, who has conceded NSW's mental health system is underfunded, said the government had made several offers to improve psychiatrists' pay and conditions in recent weeks.
That includes wage increases, conditions improvements, provisions of special allowances and duties, and a productivity pilot.
"We have comprehensive contingency plans in place to ensure people seeking mental health support continue to receive the care they need" Ms Jackson told AAP in a statement.
"The NSW government remains committed to upholding the Industrial Relations Commission's decision and we urge psychiatrists to allow the independent process to deliver a fair and reasonable outcome."
A staff specialist psychiatrist's base salary starts at $186,241, topping out at $250,000 for experienced psychiatrists.
The government's initial offer amounted to 10.5 per cent over three years.
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