SIPTU members in Trinity College Dublin have voted for strike action.
The union says the dispute is over management's failure to offer permanent contracts to staff.
SIPTU's John King says they'll meet on Wednesday to discuss their next step.
"Well we would have close to 500 members right across Trinity College in the non-academic range.
"What we're seeing is that when staff are being recruited to replace staff who have left they are being recruited on precarious forms of fixed-term and non-permanent contracts of employment," he said.