It is believed both robberies were armed
Post offices in Kilkenny and Kerry have been held up by armed raiders.
At around 12pm, a man in his mid-20s entered a premises on Main Street, Mullinavat in Kilkenny with what was believed to be a firearm.
He left the scene with a sum of money and was caught by gardaí a short distance away.
The man was brought to Thomastown garda station where he was detained under section 30 Offences against the State Act.
A sum of money was recovered.
Earlier, two men robbed Waterville post office in south Kerry.
Those involved made their escape in a navy Mazda car with an '03 D' registration.
Shots were fired by gardaí during the course of the incident, but no injuries were reported.
This car was abandoned and the suspects ran through fields on foot.
Two men in their 30s were arrested and detained at Killarney and Tralee garda stations under Section 30 of the Offences Against the State Act.
A third suspect is still being sought.
The incident has been referred to the Garda Síochána Ombudsman Commission (GOSC), as is normal practice in such situations.