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Why are my sister cats suddenly fighting and attacking each other?

Updated on September 23rd, 2025

Pet's info: Cat | Norwegian Forest Cat | Female | spayed | 4 years and 8 months old

Why have my cats (who are sisters) suddenly turned on each other and viscously started attacking the other one?

3 Answers

Most Helpful Answer

Answered By Angel Alvarado, LVT

Licensed Veterinary Technician

Published on March 2nd, 2016

It may be due to illness or injury. It can also be redirected (or displaced) aggression. This is when one cat is unable to directly respond to a perceived threat and "vents" on whoever is closest. This is usually an owner or another pet. Never handle or grab your cat if she is displaying aggressive tendencies. This can lead to a serious bite or scratch.

Schedule an exam with your vet to rule out medical causes. If they are indoor cats, provide a ' cool down' period by separating them. Keep stray or strange cats away from windows or doors and out of your yard. Control what your cat sees by closing doors or drawing the blinds. Consider using pheromone products to decrease anxiety/stress level in the house. Search www.pet360.com for pheromone products.

4Pet Parents found this answer helpful

Related Answers from Veterinarians

Answered By Amy Poole, DVM
Veterinarian
Published on January 1st, 2018
I'm so sorry to hear that Kitty seems to have a change in her behavior. I would be concerned that she may not be feeling well or potentially be in pain, causing her to be aggressive. I would recommend you take her to your veterinarian to have a full physical exam. There may be something physically wrong with her causing her to act out. If she is not spayed, I would also consider spaying her, as hormones can cause behavioral problems. If she is healthy and there is no underlying medical cause of her change in behavior, there may be something in her environment that is causing her stress. Sometimes environmental enrichment, like shelves, cat towers, etc, can help with behavior issues. Feline pheromones (Feliway) can also help some stressed cats and calm them. Finally, some cats do need to be put on behavior modification drugs, if the other previously discussed things are not the problem. You can discuss this with your veterinarian. Best of luck! I hope she is acting more friendly soon!
1Pet Parents found this answer helpful
Answered By Angel Alvarado, LVT
Licensed Veterinary Technician
Published on February 17th, 2017
Any sudden change in behavior warrants an exam with your veterinarian. Frequently, illness or injury can be the cause. It may also be some redirected aggression, especially if Bella can see or hear cats outside. If she is upset by them and can't get to them, she may strike out at whoever is close.
Once medical causes are ruled out, check your property for signs of nearby ferals or neighborhood cats. Use a pest repellant along the border of your property. You can buy a liquid or powder at most hardware or home improvement stores. Try to limit her sight from windows or doors if possible.
Try a pheromone product such as Feliway spray or diffuser to decrease any anxiety or aggression.
1Pet Parents found this answer helpful

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