The winning €38.9 million EuroMillions ticket was sold in a shop in Malahide.
Amy Cong, who owns the The Village Shop in Malahide Shopping Centre, said that never in her wildest dreams did she think she would sell a big winning jackpot ticket.
Ms Cong has run the shop with her husband Ken since 2013
She said there is an "amazing buzz" today, but has no idea who the lucky winner is.
"This is a small shop in the centre of Malahide but we are busy and we have a lot of regular customers. We have been barely able to contain our excitement since we were told by the National Lottery yesterday that we sold the ticket".
Ms Cong and her husband have another reason to celebrate as they receive a €25,000 bonus as the ticket sellers.
The National Lottery has said the winner has made contact and arrangements are being made for the claim to made, sometime in the next few weeks.
A spokesperson said the winner is getting independent legal and financial advice and "we look forward to having them come to the winner's room to collect their cheque in the near future".
Another shop in Malahide also had a lucky EuroMillions winner after a Florida-based priest home for Christmas bought a ticket at Donnybrook Fair in 22 December and scooped the EuroMillions Plus prize of €500,000.