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Why are my cats suddenly attacking one cat? What can I do?

Updated On September 23rd, 2025

Pet's info: Cat | Mixed Breed | Male | 10 lbs

My other cats (4) are attacking only one particular cat. They have never been aggresive to him before until now. They are so mean to the point they try and attack me when I separate them. This has never happened before I am not sure what to do. I separated them last night and this morning let them out to see if the separation helped. They attacked again had to reseperate. Is there anything I can do to help, or any ideas as to why this is happening so suddenly with no changes to them or environme

2 Answers

Most Helpful Answer

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Answered By Dr. Elizabeth

Veterinarian

Published on April 10th, 2019

I hate to hear that. This situation can very very stressful and it's hard to know why this is happening. It's possible Kyo is sick and his odor has changed. It may be worthwhile to have him examined by the veterinarian to make sure everything is ok. It's also possible the cats are seeing or smelling another cats outside and this is causing stress and bullying behavior. Wipe down doorways and windows to eliminate odors. Here are a couple articles to help with cat aggression and stress: https://www.petcoach.co/article/5-tips-to-handle-an-aggressive-cat/ https://www.petcoach.co/article/causes-of-stress-in-cats/ You can help relieve stress by setting aside 30 minutes a day for vigorous play for each aggressive cat, provide climbing opportunities with cat shelves and cats treats, use a pheromone diffuser and provide separate litterbox and feeding stations. Lastly, your veterinarian can provide medications or a special diet called Calm which may help the cats. Best of luck and please feel free to post any additional questions.

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Other Answers

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    Answered By Jessica Desrosiers

    Veterinary Technician

    Published on October 15th, 2018

    A sudden behavioral change can sometimes indicate underlying illness or pain, so it would be best to bring both cats into your vet for an exam to rule out any health issues as a first step. If they check out healthy, making sure both cats have their own access to food, water, litter, bedding, etc may help decrease inter-cat aggression. Adding in a pheromone diffuser such as Comfort Zone can also help with stress and aggression between cats. If the behavior continues, speaking with your vet or a veterinary behaviorist to see if additional training options or a combination of training techniques and medication is beneficial may be a good idea. You can find a list of veterinary behaviorists and more about them here: http://www.dacvb.org/about/member-directory/

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