Revenue officers say they have seized four puppies at Dublin Port.
The seizure happened yesterday afternoon after officers stopped and questioned two Irish people.
They were travelling to the UK, and did not have pet passports for the puppies.
The puppies - three male and one female Jack Russell - were not micro-chipped, as required under law.
The DSPCA has since taken the dogs into their care, and they are now receiving veterinary attention.
Puppies at Dublin Port. Image: Revenue
In a statement, Revenue said: "Revenue collaborates closely with the DSPCA and other agencies in Operation Delphin, to bring an end to the illegal trade in puppies.
"A follow-up investigation is now in progress."
Anyone with information about smuggling is encouraged to report it to Revenue's Confidential Freephone line at 1800-295-295.
