The three men, aged 24, 25 and 31, were detained following the search of a house in Letterkenny on Tuesday morning.
It follows a high-level operation in recent days by members of the Garda’s serious crime unit.
A large quantity of items was seized during the investigation.
A Garda spokesperson said the operation was “part of an ongoing investigation into a Romanian organised crime group” which is believed to also impact on the North.
Among the wide range of items seized was suspected cloned credit cards, credit cards issued in false names, bank account details, false Romanian identity documents and credit card machines.
Other items included till rolls and a number of suspected stolen Irish and UK passports and driving licences.
Two cars bought on finance obtained on bank accounts opened in false names were also seized.A Garda spokesperson said much of the seized items relate to suspected frauds in the North, adding that officers are working with Europol and the PSNI as part of the probe.
The three arrested men are currently being held at Letterkenny and Milford Garda stations.