Gardaí from Milford and the Letterkenny drugs unit have carried out a number of searches in the Kilmacrennan area.
The operation also involved gardaí in Co Monaghan and the national drugs unit.
We understand the suspect, who is from near Leitir, Kilmacrennan, was detained after a swoop on premises in Monaghan.
He is being questioned by detectives there.
The intelligence-led operation is understood to have followed pain-staking undercover investigations by gardaí.
The detained man is one of a number of people being tracked by gardaí in Milford and Letterkenny districts in recent weeks.
Gardaí across the county have found more than €1M worth of cannabis in the past six months.
Most of these finds have involved grow houses.
In September Gardaí in Milford found €250,000 worth of cannabis being grown inside premises overlooking Portsalon beach.
A Malaysian national found at the premises in Magherawarden has been charged in relation to that find.