It follows a major operation in Castlefin, senior officers have revealed.
A Garda spokesman said: “As a result of an intelligence led operation involving the Garda National Drug Unit, Customs Revenue Enforcement Officers, and the Divisional Drug Unit Donegal. Cannabis Herb with an estimated street value €400,000 (subject to analysis) has been seized in Castlefin.
“The seizure was made shortly after 8pm this evening.
“One male in his early 30’s has been arrested and is currently detained under section 2 of the Drug Trafficking Act 1996 in Letterkenny Garda Station.”
The spokesman said that investigations are continuing.
It is reported that there is a large Garda presence in the area and follow-up operations are underway.