Bus Éireann staff belonging to the National Bus and Rail Union have voted overwhelmingly for industrial action amid fears the company is planning changes to its Expressway service.
However, the ballot was described as "precautionary" and will only take effect if the company moves to implement changes to Expressway without agreement.
94% of those balloted backed industrial action.
The company has acknowledged that its Expressway service is under pressure as the National Transport Authority grants more licences to private operators.
NBRU General Secretary Dermot O'Leary accused the company of keeping Expressway workers guessing in relation to their future because of the general election.
He said speculation among staff had reached fever pitch.
Mr O'Leary added: "The current regime - along with those who have designs on governing post the election - would be well advised to heed the concerns of Bus Éireann staff, their families and the communities they serve across the length and breadth of the country as they peddle their political promises on the doorsteps."
Asked about the NBRU ballot result, Bus Éireann said: "We have no intention of taking unilateral action, so reports of an imminent strike or disruption to the business at this time, are unwarranted.
"We have always engaged with staff and unions in a two-way discussion about issues that affect the business."
"We will continue to engage with employees through our normal industrial relations process," it added.