National Bus and Rail Union members at Irish Rail have voted by a margin of five-to-one against the company's cost-cutting plan.
They have rejected pay cuts ranging from 2% – 6%, which would have lasted for up to three years.
Irish Rail said the LRC-brokered savings are essential for the future of the company, and the NBRU said it doesn't anticipate industrial action.
However, the union's General Secretary, Dermot O'Leary, warned Irish Rail workers are running out of patience.
"As recently as 2012, Irish Rail came to us with a set of proposals under the guise of the Labour Relations Commission," he said.
"Those proposals were accepted, and we got assurances back then that the company would not return for any other measures before June 2015.
So, quite obviously, our members have decided that there is a trust issue there."
Minister for Transport Leo Varadkar and Minister of State Alan Kelly issued a joint statement this afternoon on the ballot, expressing "deep disappointment".
"There have already been substantial fare increases and there is no scope for an increase in the Government subvention," the statement said.
"Therefore payroll savings are needed to protect existing service levels and jobs as part of the solutions to the financial challenges facing the company.
"Management at Iarnród Éireann will now have to consider how best to proceed with the implementation of the necessary measures. "