Cat Aggression: What Causes a Cat to become Aggressive

Do you have an aggressive cat? Are you at your wit’s end trying to figure out how to deal with them? Do you find yourself wondering whether or not you can even keep them in your household because of how aggressive they are? This article is going to be a great resource for cat aggression: what causes this behavior and how you can best handle it.

Cat aggression

George Melillo, Chief Veterinary Officer and Founder of Heart + Paw, says, “Cats are very sensitive animals and can react to subtle changes in their environment in many ways, one being to show aggression.”

Aggression in cats can be very difficult to deal with. However, this does not mean you can’t overcome this problem with your pet, especially if you are able to put in the time and effort to do so.

Types of Aggression in Cats

Cat aggression can be seen in two different ways: aggression towards other cats/animal and aggression towards humans. Each of these ways can be caused by different factors, and it’s important to know about them so you can understand what could be causing your cat to act this way. 

Read through the article below to learn more about some methods of handling aggression in cats.

Reasons for Cat Aggression Toward Other Cats or Other Animals

Some reasons why your cat may show aggression towards other cats or animals/pets include:

In Heat/Looking for a Mate

If a female cat is in heat, she may experience several mood changes, including an increase in aggression. Similarly, male cats who know a female cat in heat is in the area may become aggressive as they look for a mate nearby.

New Pet

A new pet in the family—especially a new cat or kitten—can trigger aggressive tendencies in the established cat or cats in the home. Cats may become aggressive if they feel like their established territory is threatened by a newcomer, and especially if that newcomer is very young.

Overly Rough Play

Cat aggression can come out if they’re playing too roughly. Kittens learn how to play a little bit roughly, and they may need older cats to teach them how to tone it down.

However, if a kitten is taken away from their mother too early, they may not have the chance to learn how to play politely. Their rough play may appear aggressive to human family members.

Territory Disputes

Cats are extremely territorial and may get into aggressive fights with each other over their territories. Although this problem is common with outdoor cats, it can happen with indoor cats who don’t have enough space to themselves, too. Indoor cats need their own sleeping spaces, separate litter boxes, and separate food dishes to prevent this type of aggression from happening.


Aggression in cats can also be caused by fear. Cats who are afraid of other animals in the household may react with aggression. A fearful cat is likely to scratch and bite to defend themselves. Cats who are afraid of large dogs in the family, for example, may be prone to this type of aggression.

Prey Animals

If you have any pets in your household that can be seen as prey animals, such as rodents, reptiles, or birds, your cat may appear very aggressive toward them. This is likely because they are acting on their natural instincts and could be trying to hunt them.

Reasons for Cat Aggression Toward Humans

As previously mentioned, it’s not uncommon for cats to show signs of aggression towards humans, either. The causes for this behavior are different than if they’re being aggressive towards other animals or pets, but they’re just as important to know.

5 common reasons for cat aggression towards humans are:

Protecting Their Kittens

Mother cats are very defensive of their kittens. If you have a mother cat with a recent litter of kittens in your household, human family members may want to stay away from her as much as possible. She may become very aggressive toward anyone who approaches her, and especially those who approach her kittens.

Pain or Illness

A cat who is in pain is likely to become aggressive and defensive. The same is true of a cat who is very sick. If your cat shows signs of being in pain or being sick and is aggressive at the same time, take them to the veterinarian as soon as possible for proper treatment and care.

Over Stimulation

If your cat is over stimulated, they may become angry and aggressive. Over stimulation occurs often when cats are petted for too long, but it can also come from too much play, too much noise, or too much interaction with other members of the family.

Redirection of Anger

Aggression in cats can stem from them redirecting their anger to another source. Cats may sometimes take out their aggression and anger on human family members as a redirection from the source of the problem.

For example, if your cat sees another cat out the window and you go to pick them up, they may angrily lash out at you with their claws as a response.

New Baby

If you bring home a new baby, your cat’s whole world will quickly be turned upside-down. This can sometimes trigger aggressive behavior in cats who are otherwise fairly docile and calm. Your cat may be aggressive toward the baby, but is much more likely to take out her aggressions on the adult members of the family who are still interacting with them.

What to Do if You’re Concerned about Cat Aggression

As always, a veterinarian will be the best person to consult when trying to figure out your pet’s behavior. If your cat is aggressive because they’re in pain or because of other environmental factors, your vet will be able to help rule out any potential health causes and will be able to guide you on the best path to helping your pet.

Learn More about Aggression in Cats

With the help of this information, you should be well on your way to better understanding your cat’s aggression and finding ways to work through it. Remember, however, that there is no shame in working with a trainer, and if your cat does not respond to your own training methods, a professional may be required.

With the help of a professional trainer, you can get to the bottom of your cat’s aggressive tendencies and work through them as well. Your vet may also be able to suggest some methods that can help, especially when your cat is aggressive toward the members of your family.

For more information about cat aggression, or if you have other questions about your pet’s health or behavior, contact any of our Heart + Paw locations today. You can book an appointment with our team, who will provide you with the best advice for your pet and will make sure they remain as healthy and happy as possible. 

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Heart + Paw was founded in 2018 by Chief Veterinary Officer Dr. George Melillo, who currently serves the Mid-Atlantic area. Heart + Paw offers a combination of veterinary care, pet grooming, and dog daycare to help be a resource in your pet parenthood journey.

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