Get

In Your Inbox

Catster is reader-supported. When you buy via links on our site, we may earn an affiliate commission at no cost to you. Learn more.

Why Is My Cat Suddenly Aggressive? Vet-Reviewed Reasons

kittens training

It can be extremely disconcerting for your cat to suddenly begin to exhibit behavior that is unusual for them, especially if your once sweet kitty has suddenly become an aggressive monster. There are a few reasons that cats may suddenly become aggressive, from fear and stress to another intact cat nearby. It’s important to understand why your cat’s behavior has suddenly changed so you can start working to fix the problem.

divider cat faces oct 2024

 

Why Is My Male Cat Suddenly Aggressive?

Breeding

Male cats don’t like competition when it comes to selecting a mate, and it’s extremely common for tomcats, or intact male cats, to fight with each other for breeding rights in a certain area. When a female cat is in heat, you can expect multiple males to show up to breed with her, so there’s a likelihood that you’ll spot a few tomcat fights during this time.

Health Conditions

Pain and discomfort from health conditions can lead to aggression in normally pleasant cats. Although there are many potential causes of pain and health problems, male cats, in particular, are at a high risk for developing feline lower urinary tract disease, or FLUTD. This condition can lead to obstructions of the urinary tract, leading to an inability to urinate, extreme pain, and even bladder rupture.

aggressive cat
Image By: pixbull, Shutterstock

Why Is My Female Cat Suddenly Aggressive?

Breeding

The behavior of a female cat can change significantly when she is in heat. Typically, female cats will become extremely loving and attention-seeking. However, some female cats may become irritable and aggressive due to their hormonal changes. They may also show more aggression than normal to other cats, especially females.

Health Conditions

Like male cats, female cats can also express pain and discomfort through aggression. Female cats may experience infections and cancers of the reproductive system, including pyometra, mammary cancer, and ovarian cancer. These conditions may lead to changes in your cat’s hormone levels and comfort level, leading to aggressive behavior. If you notice this in your cat, you should reach out to a veterinarian for the consultation.

If you need to speak with a vet but can't get to one, head over to PangoVet. It's an online service where you can talk to a vet online and get the advice you need for your pet — all at an affordable price!

PangoVet_Mention-in-Content for PangoVet2 save money

divider cat faces oct 2024

The 6 Other Causes of Sudden Aggression in Cats

1. Fear

If your cat is startled, they may respond with aggression until they process the situation and realize they’re safe. Cats that constantly live in a high-stress environment that makes them feel unsafe may become aggressive all the time. Cats should always be provided with a quiet, safe, comfortable place to get away from everyone and everything if needed.


2. Play

Some aggression in cats isn’t truly aggression at all. Playtime for cats is a way for them to hone their hunting skills, so it only stands to reason that your cat may start to play too rough, crossing over into aggressive behavior. This behavior can be remedied through positive reinforcement and aggressive, overly rough play should not be allowed since this can lead to injuries.


3. Territory

Some aggression in cats can arise when a new cat (or dog) enters their territory. This may be a new housemate that has been brought into the home, or a new outdoor cat that is coming around for visits, potentially unknown to you.

aggressive cat in a cage
Image Credit: Anna Krivitskaya, Shutterstock

4. Redirection

When cats are frustrated, they may lash out, showing aggression toward you or other animals in the home.


5. Dominance

Cats tend to establish social hierarchies, and therefore when new additions enter their house, the social structure may change. This can lead to aggression, as the new social rankings are established.


6. Petting

We’ve all likely experienced that odd behavior where a cat will seem to be asking to be petted, but once you do it, they bite and scratch. Why do cats do this? In all honesty, nobody really knows exactly why. It’s possible that they become overstimulated by too much touch, or maybe they simply want to be near you without being petted. Either way, it’s important to avoid touching your cat when they seem agitated. Reward them with tasty treats when they allow you to pet them without incident.

divider cat faces oct 2024

In Conclusion

Approximately 8% of animals surrendered to animal shelters in the US were surrendered due to aggression. Many of the causes of aggression in cats are manageable, but they do take time and effort to work through. If you don’t want your cat to become a statistic, make sure to focus on positive reinforcement of good behavior while discouraging aggression and other undesirable behaviors.

Also see:


Featured Image Credit: Anatoliy Cherkas, Shutterstock

Want content like this delivered to you?

Sign Up For Our Newsletter

News, insights, expert advice, and everything cat

* By submitting, you agree to our Terms & Conditions and Privacy & Cookies Policy.

How useful was this post?

Click on a star to rate (you can leave written feedback after clicking submit)

Help us improve Catster for pet parents!

Your feedback really matters.

What did you like about this post? Also how can we improve it?

Join the conversation

Leave a Reply

You’re very welcome to leave a comment or question. Please know that all comments must meet our community guidelines, and your email address will NOT be published. Let’s have a positive and constructive conversation.

Talk With A Vet Online

Peace of mind,
anywhere, anytime

Affordable vet advice

How to Find a Cat-Friendly Vet: 5 Vet-Reviewed Steps

If you’ve just moved or recently adopted a cat, and you’re looking for a vet to take them to for their checkups and...

How to Give a Cat a Head Massage: 4 Vet-Reviewed Tips & Benefits

You wouldn’t think giving a cat a head massage would be something your feline would like, but you would be surprised. While not...

How Do Cats Hunt Mice at Night? Vet-Approved Cat Behavior Guide

We all know the relationship between cats and mice. If a mouse is in your house, whether your cat is the world’s laziest...

How to Tell if a Cat Is Microchipped: 4 Vet Approved Signs to Look For

If you find a stray cat with no obvious identification, finding the owner can be challenging. Feral cats typically stay away from people...

More related

Can Cats Eat Cake? Vet-Reviewed Risks & Facts

Cats are adorable. We understand why you’d want to share a piece of cake with your kitty. Since cakes are often found in...

Ask Dr. Paola – Refusal to Eat, Over-Grooming, & Dog Medicine (February 24, 2025)

Welcome to our “Ask Dr. Paola” series, where every Monday we bring expert advice straight from Dr. Paola Cuevas (MVZ) to help our...

Introducing Milly the Sassy Rescue and Her Owner Isabel (with Video)

Welcome to the Wednesday Cats of Catster! Every week, we share a story from one of our cat-loving Catsters. This week is about...

Cat Respiration Rate: How Fast Should My Cat Be Breathing?

You may notice your cat sleeping peacefully next to you and breathing rapidly — or so it seems. Exactly how fast should a...

Keep reading

Can Cats Eat Gummy Bears? Vet-Reviewed Nutritional Facts

Gummy bears are fun treats when you want to wind down after a long day. They’re chewy, sugary, and adorably tasty. If your cat is the sort to always demand a nibble of whatever you’re eating, you may have considered...

Can Cats Eat Gummy Bears

Is It Ok to Put Ice Cubes in a Cat’s Water Bowl? Vet-Reviewed Pros & Cons

Most cat owners know that keeping a cat hydrated can sometimes be a challenge. Hydration is important for cats, and it’s even more important in the hot summer months. However, getting a cat to drink water is not always easy,...

Woman putting ice cubes into pack

Top 9 Healthiest Cat Foods in 2026 (Top Ingredients & Brands)

We all want our cats to be as healthy as possible and part of that comes from choosing the correct food for our cats. For our cats to be as healthy as possible, we need to select the healthiest food...

cat eating kibbles from red bowl

Cat Splashes Water Out of the Bowl: 5 Vet-Verified Reasons & How to Stop It

While the behavior can be frustrating due to the mess, your cat splashing their water out of their water bowl and all over the floor is normal and usually no reason for concern. Despite having a reputation for being afraid...

a cat dipping its paws on a bowl of water

Can Cats Drink Bone Broth? Vet-Approved Nutritional Facts & FAQ

Bone broth has become a very popular topic of conversation for pet owners. It is being touted as a more natural way for cats to get key nutrients. Some people even claim that drinking bone broth brings cats back to...

Can Cats Drink Bone Broth

Are Hydrangeas Poisonous to Cats? Common Houseplants Examined

Hydrangeas are beautiful blooming flower bushes that are a stunning addition to any home garden. If you have cats, however, you should tread with caution when planting these gorgeous blooms in your yard. All parts of the hydrangea plant are...

Catster_Are Hydrangeas Poisonous to Cats

How Can I Soothe My Cat’s Itchy Skin: 9 Natural Home Remedies

If you notice that your cat is scratching incessantly, losing hair, or developing a rash, they are likely having an allergic reaction. Skin allergies are fairly common in cats, affecting around 10% of felines, with causes ranging from fleas to...

cat itchy

9 Best Tartar Control Products for Cats in 2026 – Reviews & Top Picks

Every cat owner knows that their feline companion can spend hours upon hours grooming themselves, but one area they can’t clean is their teeth. Dental hygiene is paramount to the health of your cat, and the smell of your cat’s...

tabby maine coon teeth brushing