Revenue officers seized €7,000 in Rosslare Europort on Thursday.
Following routine profiling, Revenue officers - with the assistance of detector dog Flynn - stopped and searched a vehicle that had disembarked a ferry from Cherbourg, France.
Revenue said that on Friday, at a special sitting of Gorey District Court, they were granted a three month Cash Detention Order.
"The cash is suspected to be the proceeds of, or intended for use in, criminal activity and is detained by Revenue in accordance with proceeds of crime legislation," Revenue said in a statement.
"A man originally from Latvia but now living in Ireland was questioned. Investigations are ongoing."
They added that "these routine operations are part of Revenue's ongoing work targeting smuggling and shadow economy activity.
If businesses, or members of the public have any information, they can contact Revenue in confidence on Confidential Phone Number 1800 295 295.