Psychologists working across the nation's 17 district health boards have voted to refuse working overtime for five weeks as part of strike action.
Members voted in favour of the first nationwide strike for psychologists in New Zealand after DHBs failed to address the workforce crisis.
The union for health professionals, Apex, said the strike would start on July 31 and run until September 3.
Consultant clinical psychologist Annmarie Kingi said issues within the sector have been long-standing and are ongoing.
"There's little scope for leadership across the board, we're overworked, got very complex clients on our caseloads, wait lists," she said.
"It's about the lack of focus to valuing the workforce and recruitment and retention issues - they've been long-standing and it's just growing."
Having worked in the industry for the past 15 years, Kingi said psychologists just want to see offers of better pay and work conditions than what is currently on offer.
Meanwhile, the Ministry of Health deputy director - general health workforce Anna Clark said it wasn't able to comment on pay negotiations.
"We do note that DHBs settled a Meca (Multi Employer Collective Agreement) last year with the Public Service Association for its allied health workers, including psychologists," she said.
"Budget 2019 included a further $213 million increase in the DHB funding specifically allocated to mental health.
"It's acknowledged that the Government's commitment to mental health will require a significant expansion of the relevant workforces."
However, Clark told the Herald that supporting the development of career pathways for psychology was a priority for the ministry.
Apex said the international benchmark for health services is that they employ 20 full-time psychologists per 100,000 people.
New Zealand DHBs employ an average of 11.8 psychologists per 100,000 people.
In 2018, the Ministry of Health and Health Workforce New Zealand set up the Psychology Workforce Taskforce which said an extra 268 psychologists were needed for DHBs to meet demand.
"Yet in the same year, rather than gaining, we lost 73 psychologists from DHB employment," Apex national secretary Dr Deborah Powell said.
"DHBs are losing experienced psychologists in droves to better-paid jobs in the Department of Corrections, ACC and private practice."
Kingi said for recent psychology graduates, the appeal to work elsewhere, like the Department of Corrections, was much higher than public health.
"If you look at just the Government sector the pay options and working conditions are better at the Department of Corrections," she said.
"That is a really good starting point in your career and the trouble is, once you get there you have to essentially take a pay cut to come into mental health if you want a change."
Psychologists are employed in DHBs and offer a range of mental health services including forensic services, community mental health and addiction services.
They also work in physical health services, including cancer, cardiac, spinal, diabetes and older persons' health.