Seven million contraband cigarettes worth 2.7 million euro have been seized by customs officers.
The haul of Raquel and Capital brands arrived in Dublin Port from Zeebrugge in Belgium in a shipment described as "non-hazardous groupage".
They were discovered by officials when the consignment was routinely scanned by the mobile scanner.
An Irish registered commercial vehicle and trailer were seized and the driver was interviewed.
A Customs spokeswoman said investigations are ongoing both nationally and internationally.
The seizure had a potential loss to the exchequer of 2.4 million euro.
"This seizure is part of Revenue's ongoing operations targeting the smuggling and sale of illegal cigarettes," said the spokeswoman.
"This latest seizure brings the total number of cigarettes seized by Revenue to date in 2012 to 66 million, with a retail value of 28 million euro.
"If businesses or members of the public have any information regarding the smuggling or sale of illegal cigarettes, they can contact Revenue in confidence."