The baby cats – thought to be aged between three and five weeks old – were discovered by a veterinary nurse as she made her way to work on Saturday morning in Dagenham, Essex.
Whoever dumped the youngsters had poked small air holes in the suitcase so that they could breathe.
The ‘Suitcase Kittens’ – who are believed to have come from up to four separate litters – are now being cared for by volunteers from Cats Protection’s Hornchurch and District Branch.
Welfare & Homing Officer Alison Gambles said: “Although they were all alive and in fairly good condition, they were clearly far too young to be away from their mothers.
“Six of them had obvious cases of eye infection and although the others seem okay for now, we will need to closely monitor them.
“Someone must have felt in a very desperate situation to do this.
“They seem to have intended the kittens to be found as the suitcase had been left near the home of the veterinary nurse, who is well known locally.
“But with kittens this young and vulnerable, the outcome could have been awful.”
The kittens will now be hand-reared by staff at the rescue centre before they are adopted by new owners.
Alison added: “Suddenly acquiring 15 new kittens to care for is a huge drain on our resources.
“Although we have already got owners lined up for them, we will need to care for them until they are old enough to be homed.
“What’s more of a challenge is that many people find kittens a lot more desirable, so the many young adult cats we have in our care will now wait longer to find a new home.”
Head Vet at Vets4Pets in Dagenham, Debra Teo, where the kittens were initially taken, said: “We are pleading with all cat owners to have both male and female cats and kittens neutered.
“The current situation could so easily have been averted and also could have easily ended up being a tragedy.”
Cats Protection are now appealing for the owner of the kitten to get in touch to discuss how to prevent more unwanted cats from being born.
Top pic: Facebook/Cats Protection Hornchurch