SIPTU Health Sector Organiser Paul Bell said around 4,500 support staff would withdraw their labour from 1am on Wednesday 7 April until 1am on Friday 9 April.
He said the union had given the Government four weeks' notice to give them time to return to talks.
The hospitals affected if the strike goes ahead are Beaumont Hospital, Mater Misericordiae University Hospital, Tallaght Hospital, St Vincent's University Hospital, St James's Hospital, Connolly Hospital Blanchardstown and St Columcille's in Loughlinstown.
The grades involved include porters, catering personnel, security, healthcare assistants and supervisors.
Mr Bell said that low-level action was also anticipated for ambulance services in counties Dublin, Kildare and Wicklow.
He warned that other hospitals in Dublin would have similar disputes in the weeks after the initial work stoppage.
He also said that hospitals not on strike in Dublin would be organising a solidarity fund to support striking workers.
Mr Bell said the four weeks' strike notice would allow employers time to engage in meaningful dialogue with SIPTU on the issues in dispute.
The issues include the refusal of hospital management to honour the terms of the 'Towards 2016' pay agreement and over what he said was the threat to outsource the jobs of union members.
The HSE has said it has yet to receive the formal notice from SIPTU.
In a statement it said: 'If and when we do receive that formal notice, we would expect the unions to comply with our agreement for procedures on emergency cover.
'We would also bring our human resources managers from the hospitals together with SIPTU to agree contingency arrangements.'
