Almost 7,000 health and social care workers in bodies funded by the Department of Health have voted overwhelmingly to take strike action over the failure to restore their pay cuts in line with public servants.
SIPTU said that that 97% of staff balloted had backed strike action, which will begin with a one-day stoppage on 14 February.
The turnout was 85%.
The dispute centres on around 12,000 workers in bodies known as Section 39 organisations, of whom SIPTU represents around 7,000.
Section 39 bodies are funded by the Department of Health, but staff are not deemed to be public servants.
They care for some of the most vulnerable service users in the health and social care services.
In 2010, funding allocations to Section 39 bodies were cut in line with the public service austerity pay cuts, forcing them to cut staff pay.
However, while public servants have seen significant restoration, the Section 39 funding allocations have not been boosted to permit restoration for their staff without hits to services.
SIPTU members say they will strike on 14 February if the dispute is not resolved in the meantime.
SIPTU Health Division Organiser Paul Bell said staff would not settle for less than full restoration in line with public servants and other organisations.
However, he also warned that if their demands are not met, staff are prepared to take further industrial action.
Speaking on RTÉ's News at One, Mr Bell said: "What we need now is real dialogue, a real process to try and ensure that people receive pay justice and those relying on those services in the various communities throughout the country are not disrupted.
"And that we can somehow understand that these people can be treated equally."
The Department of Health said in a statement that a process is being finalised to establish the factual position regarding pay reductions and pay restoration in the Section 39 organisations.
The statement added: "Whilst it is understood that pay cuts were implemented in many section 39 organisations, it is not clear if these cuts were applied in a universally consistent manner across all section 39 agencies.
"So while staff may have been subject to cuts, it is not known if the cuts were to the same extent as those applied to public servants. There are significant cost implications to be considered."
Asked about the Section 39 strike and pay restoration issues, the Department of Public Expenditure and Reform said it was a matter for the Department of Health.
The Health Service Executive also referred queries to the Department of Health.