Gerard Colhoun from Munitirtinney, Raphoe was sentenced by Judge John O'Hagan at Cavan Circuit Court today.
Colhoun was jailed for 5 years today for possession of heroin for sale and supply.
Colhoun was suspected to be selling and supplying heroin in the Letterkenny and greater Donegal areas.
As a result the Letterkenny drugs unit set up an operation in 2010.
On 22 April, 2010 was intercepted by Gardai when he was making his way back from Cavan to Donegal, he was found to be in possession of heroin with a street value of €19,000.
A spokesperson for Letterkenny Garda station today said it was significant that Colhoun had been "taken out of the loop".