The man burst into the post office in Blarney at around 1.45pm yesterday and demanded cash from a female member of staff.
Gardaí believe that he had cased out the post office and before striking may have parked his getaway car close to the entrance to the former Blarney Park Hotel.
A Garda spokesman said that the getaway car was believed to be a 1999 or 2000-registered Toyota Avensis.
“It was dark in colour and had some silver [possibly water deflectors] on the windscreen wipers,” the spokesman said.
He described the armed robber as around 5ft 7ins tall.
“He had a black, woolly hat on and a Liverpool-style jacket with blue Adidas-type jacket, and he also wore pointed winkle-picker type shoes,” the spokesman said.
He said that the raider appeared to be armed with a sawn-off shotgun when he threatened the member of staff.
Fortunately, the woman was not injured, but was said to be shocked by the ordeal.
Gardaí are looking at CCTV footage in the area in the hope it will shed light on the identity of the raider and what roads he may have taken when he made his escape.
They are also carrying out inquiries in the village.
“We are anxious to hear from anybody who may have seen this man in the Toyota Avensis either before or after the robbery.
“We are particularly interested in speaking to anybody who saw the car after it left Blarney village,” the spokesman said.
Anybody with information is asked to contact Blarney Garda Station on 021 4516290, Gurranabraher Garda Station on 021 4946207, or Anglesea Street Garda Station on 021 4522000.