Revenue officers at Portlaoise Mail Centre have seized drugs worth €27,000.
The discovery followed routine profiling on Tuesday.
Some 54kgs of khat was seized by officers.
The drug was found in a number of parcels which came from Ethiopia and Kenya.
The parcels, some of which were declared as 'clothing', were destined for various addresses in Dublin city.
Officers say investigations are on-going with a view to prosecutions.
Khat is a stimulant, with similar effects to amphetamine, which comes from a leafy green plant of the same name.