The Psychiatric Nurses Association says it will strike in Roscommon, Galway and Mayo until every graduate nurse in the region is offered a HSE contract.
Targeted industrial action is beginning this morning, following a meeting of the PNA board.
The action will take the form of a work to rule by nurses in the areas affected.
According to the association, only half of the required psychiatric nurse graduates for the area have been recruited.
PNA General Secretary, Peter Hughes says this is not acceptable: