Customs have seized more than 12 million counterfeit cigarettes with an estimated retail value of 3.6 million euro.
In an operation on Thursday night, officers, backed up by gardai, seized a 6m container marked "Alloy wheels" and a van with around four million Marlboro Light cigarettes.
The container arrived at Dublin Port from China.
A man detained at the scene was later released and a file is being prepared for the Director of Public Prosecutions.
In a second operation, officers at the capital's port seized a 12m container with around eight million John Player Blue cigarettes, from Singapore.
The container had been marked "Instant noodles".
Lobby group Retailers Against Smuggling said the seizure revealed the Government was right not to increase the price of cigarettes in the Budget.
Spokesman Benny Gilsenan said: "Tobacco is a vital part of the income of every single Irish retailer.
"We sell a legal and legitimate product but when national and international criminals can sell the same product on the street for less than half the price, there is no way that we can compete."