Drivers on Arriva Trains Wales have voted overwhelmingly for strike action in a dispute over pay and conditions.
The Rail Maritime and Transport (RMT) union said 85% of members backed the industrial action
RMT General Secretary Bob Crow described the company's offer as "paltry". He added: "It would have left our members out of pocket and which was loaded with strings.
Arriva Trains Wales (ATW) said it was "surprised and disappointed".
But Mr Crow said: "Our members would have ended up with inferior working conditions for a de facto pay cut.
"Arriva Trains Wales have shown us in the clearest possible terms that they have no wish to properly reward the hard work and loyalty to the staff and are motivated solely by the drive for bigger profits to line the pockets of the shareholders
"That is why we have balloted for industrial action and why our members have delivered this overwhelming mandate," Mr Crow added.
Last month a planned stoppage at Arriva Trains Wales by members of the drivers' union Aslef was called off.
An ATW spokeswoman said: "We are surprised and disappointed that the RMT has chosen to ballot for industrial action, based on a previous pay offer which has since been superseded by a significantly improved offer."
The spokeswoman added that ATW train drivers were represented by two trade unions, ASLEF & RMT, and that ASLEF had recommended the latest pay offer to its members for acceptance.