Around 100 nurses have taken part in a protest at St Vincent's Hospital in Dublin.
The nurses are highlighting overcrowding in the Emergency Department, saying they believe they have "no option but to highlight the unacceptable conditions" at the hospital.
A work-to-rule will begin from 8am tomorrow morning.
Philip McAnenly from the Irish Nurses and Midwives Organisation says the hospital needs to start prioritising patients - and emergency cases should be seen first:
Members of the Irish Nurses and Midwives Organisation say there has been a failure to acknowledge the problem and the number of patients on trolleys in the ED is being understated.
Management at the hospital say they deeply regret the decision of nurses to embark on industrial action.
Nurses chose to ballot “following months of overcrowding inevitably leading to increased risk to patients and intolerable conditions for nurses," Mr McAnenly said.
"INMO members believe they have now no option but to highlight the unacceptable conditions patients are being subjected to. The decision to commence industrial action, up to and including withdrawal of labour, seeking immediate improvements, to protect both patients and themselves, has been unanimous.”