Detectives said two firearms were also seized when they stopped the men in two cars in Kill, Co Kildare.
The Garda's Organised Crime Unit was backed up by the armed Emergency Response Unit during the stop and search around 1am on Sunday.
The five men, all in their 30s, have been taken to Clondalkin and Ballyfermot Garda stations and are being detained under section 30 of the Offences Against the State Act.
The firearms have been sent for ballistics tests.
