SIPTU has served strike notice on the Arnotts department store in Dublin over its plans to move storage facilities out of the city centre.
The union says 57 of its members who work in the company's stockroom are unhappy with the planned move to Tallaght.
It has also accused management of attempting to impose a new shift pattern on workers without consultation.
SIPTU says it has yet to decide what form of industrial action to take, but it could include a work-to-rule protest, a refusal to do overtime or an all-out stoppage with pickets.
The action will begin in two weeks' time unless talks at the Labour Relations Commission can resolve the matter.