Woolworths in Londonderry employs 50 people
Woolworths' administrators have begun efforts to rescue the chain, which has 19 stores in Northern Ireland.
About 200 jobs are under threat here, but administrators Deloitte have said the stores will remain open until after Christmas and staff will be paid.
The chain, which has 815 stores and 30,000 employees nationwide, collapsed under £385m of debt.
The MFI furniture chain has also gone into administration, affecting its three stores and 60 staff in NI.
It is understood staff have been asked to stop taking orders at its stores in Spucefield, Bangor and Newtownabbey.
Eighty jobs are under threat at two Woolworths stores in the north west.
The high street retailer employs 50 staff in Londonderry and a further 30 in Strabane.
John Gorle from the trade union USDAW, said the "only option" was to find a buyer.
He said he understood there were "parties making their interest known to the administrators".
Former Woolworths manager Sean Trainor said it was a "blow to everyone".
"Woolworths were certainly very much part of town centres throughout the Troubles and survived and came back again and traded very strongly," he said.
"Unfortunately, their trading patterns over the last four to five years have been declining rapidly."