Gardaí say that a gunman wearing a balaclava entered the premises on Cork Street in Dolphin's Barn at around 11pm last night.
He shot the 66 -year-old victim in the leg before escaping.
The injured man was taken to St James' Hospital for treatment and his condition is not believed to be life-threatening.
Gardaí have preserved the scene for a technical examination.
Gardaí wish to appeal for witnesses who were in the area at the time of the shooting to contact Kevin Street Garda Station on 01 – 6669400, The Garda Confidential Telephone Line 1800 666 111 or any Garda Station.