The union said the dispute was over a pay offer of 4.1 per cent, which it pointed out was less than half of the current RPI inflation rate.
Workers being balloted include bus drivers and engineers, based at depots in Castleford, Dewsbury, Heckmondwike, Selby and Wakefield.
Unite said many of the bus drivers were struggling to make ends meet because of the cost-of-living crisis.
The ballot will close on May 23, so strikes could begin in early June if there is a yes vote.
Unite general secretary Sharon Graham said: "This offer is a pay cut and is unacceptable to Unite. Arriva has to think again and come back with an offer that fully reflects this cost-of-living crisis."