The man in his late 20s is stationed at a Garda station in the city.
He was arrested at his home in County Cork early this morning and taken to Cahir Garda station in County Tipperary where he can be held for up to 24 hours.
It's understood the arrest comes on foot of an investigation into the sending of a number of anonymous letter to senior Gardaí and GSCO.
The letter contained false allegations of misbehaviour by Gardaí.
It's believed the Garda began sending the letters either late last year or early this year and that the letters were sent to Garda management over the course of several months.
