The kitten suffered irreparable damage in the event.
An animal charity based in County Cavan were left horrified as they found a kitten squished through their post box.
Writing on Facebook, the Cavan SPCA Charity Shop shared: "So this morning we discovered this gorgeous wee kitten in our shop after some cruel individual decided it was a good idea to shove her through our (very small) letterbox.
"Due to this person's actions this wee baby has now been put to sleep after the vet discovered she had severe irreparable internal damage."
"This is beyond shocking & the wee kitten would have suffered terrible pain being forced through a letterbox a fraction of her size... This will be reported to the guards so we can find the culprit", they added.
The person responsible for the damage inflicted on the kitten has not yet been found.