Members of the NBRU at Dublin Bus have voted by over 96% in favour of industrial action.
Ballots of other unions at the company are also expected to produce votes in favour of strike action.
Bus stoppages are expected by the end of the month, unless a resolution can be found.
Drivers at the company are seeking pay parity with Luas drivers.
NBRU General Secretary Dermot O'Leary says the ballot followed a recent Labour Court ruling: