A garda based in Co Kerry is being questioned by investigators from the Garda Síochána Ombudsman Commission in relation to an allegation of drug dealing.
It is understood that the garda is being questioned at Mallow Garda Station in north Co Cork following his arrest this morning.
Under the 2005 Garda Síochána Act, GSOC investigators have the same powers as gardaí when they are investigating an allegation of a criminal offence against a garda.
The garda can be held for up to 24 hours.
A spokesman for An Garda Síochána said he was precluded from commenting and a spokesperson for GSOC declined to comment.