Nursing staff at St Ita's Hospital in Portane, Co Dublin have voted overwhelmingly in favour of industrial action up to and including strike action.
The action is in protest at what they say is the growing impact of staff shortages at the St Joseph's Centre for Intellectual Disability within St Ita's.
84% of the 440 members of the Psychiatric Nurses Association balloted voted for action, with 7% against.
The action will be on a phased basis.
It is due to begin on Friday 21 August at St Joseph's centre.
The HSE has said it has not yet been formally notified of the outcome of the ballot.
In a statement, it said: "The safety and ongoing care of our residents in St Joseph's Intellectual Disability Services is an ongoing priority for the HSE.
"HSE Management have been working closely to mitigate any risks due to staffing vacancies at St Ita's Hospital. A number of actions have been taken including maximising the use of all agency nursing staff and the nursing bank. There is also an active focus on recruitment to fill the vacancies.
"Management in the HSE will actively continue to engage with the unions and staff to resolve the issues."
