Kings Pharmacy is set to close for good on Thursday.
The chain is the only pharmacy in Ireland with a direct competitor in the country, which has more than 1,000 pharmacists.
The closure is the latest setback for the chain, which was established in 2011.
Its loss of a fifth of its business is one of the biggest in the Irish pharmacy industry.
The move comes as the company is in talks with its Irish partners about buying a 50 per cent stake in another pharmacy chain.
It is understood the sale is not likely to happen until the end of the year.
However, the company has been struggling to keep up with the rise of online pharmacies, which are also competing for the same customers.
The company has faced pressure from rivals like CVS, which is in the process of closing down its Irish division and will likely continue to do so in the coming years.
Last week, it confirmed it was seeking to sell its majority stake in the Dublin-based company to its Irish partner, Oupa.
Its decision comes at a time when the Irish pharmaceutical industry is facing a new wave of competition from online pharmacies.