Gardaí in Letterkenny, seized suspected cocaine, cannabis, and cash during a search operation as part of Operation Tara.
The Donegal Divisional Drugs Unit, with assistance from the Armed Support Unit, executed a search warrant at a property.
The seized drugs are estimated to have a street value of €2,800 for cocaine and €1,200 for cannabis.
Gardaí also recovered €1,900 in cash and £230 in sterling.
A man and a woman, both in their 20s, were arrested and are being held at a Garda Station in Donegal under Section 4 of the Criminal Justice Act 1984.
Investigations are continuing.