The Mandate trade union has claimed that over 100 jobs are to go at Dunnes Stores in Gorey.
The body said that workers were called to a meeting this evening where they were told that the outlet is to close.
Dunnes Stores has not been available for comment this evening.
General Secretary of Mandate John Douglas has said that workers are very concerned.
"Our members were called in this evening just before they finished their shifts to be told that the store was closing," said Mr Douglas.
"It is a modern store in a modern shopping centre and they were given no explanation other than that the company would cease trading from this evening. There are over 100 workers in the store and they are extremely concerned."