Five units of Cork City Fire Brigade tackled a blaze at a store on Castle Street in the city in the early hours of Thursday morning.
The fire at computer repair and retail outlet IT Central broke out some time before midnight onWednesday. The cause of the fire is not yet known.
Fire fighters left the scene at 5am on Thursday, having stayed at the site for an additional period as a precautionary measure to ensure the fire was fully extinguished.
The two premises on either side of the shop were also damaged in the fire.
Gardaí have confirmed that a man at the scene was treated for smoke inhalation. He was not seriously injured and is in a stable condition.
Castle Street remains closed as Gardaí and fire services carry out a full technical examination of the site.