Gardai at Dublin Port have rescued 26 puppies and seven adult dogs following a search of two vehicles.
The animals were found late on Sunday evening by members of the garda Immigration Unit.
Gardai had concerns about the dogs' health and the manner in which they were being transported.
The drivers of the vehicles were unable to produce any proof of ownership, pet passports or vaccination/microchip certificates.
Following further investigation, all the dogs were seized and are now in the care of the Dublin Society for the Prevention of Cruelty to Animals (DSPCA).
They have been undergoing extensive heath checks and follow-up veterinary treatment.
Included in the seizure are two litters of very young Jack Russell puppies, about two weeks of age, travelling with their mothers.
One of the female dogs is also heavily pregnant.
Some of the dogs are infested with fleas, some are of a poor body weight and one of the puppies had an infected umbilical cord.
There are also concerns that some of the puppies have had their tails docked.
This case is under investigation by gardai and the DSPCA are not in a position to foster or rehome these dogs at this time.
In a statement, the charity said: "The DSPCA would like to thank the gardai at Dublin Port for their diligence.
"We would like to remind the public that we are still working to care for animals in these difficult times."
The society is urgently appealing for the public to donate to help them care for the dogs.