Staff at the EBS building society have voted overwhelmingly to take strike action during Christmas week.
The workers are angered by the company's decision to withhold a "13th month" bonus payment, which the UNITE union said has been paid annually for the past 45 years.
A total of 98% of those balloted were in favour of the industrial action.
EBS has received around €2.4bn in state bailout funds to date.
It is now part of Allied Irish Banks, which prohibits bonus payments under the terms of its bailout agreement with the Government.