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

Is Jasmine Poisonous to Cats? Vet-Reviewed Houseplants Examined

Most of us love the look of live houseplants and gorgeous, colorful gardens. However, many of these plants can pose an unexpected threat...

Are Sunflowers Toxic to Cats? Vet-Verified Facts & Safety Tips

Bright, colorful, and towering far above most of our heads in their natural growth state, sunflowers are the kind of bloom that makes...

How to Help Cats Adapt to a Divorce: Vet Reviewed Techniques & Tips

Divorce is never easy, and it’s even more complicated when pets are involved. Cats like their routines, and they get attached to their...

Catster Photo Contest: Cats of the Week Winners (November 13, 2025)

Every week our team gets the privilege of sorting through our readers photos to choose what cats will win this weeks contest! See...

More related

Are Kuppies Real? Can Dogs & Cats Crossbreed? What Science Says

Tales from all over the world have been told of some seemingly impossible things happening on our planet. You are sure to have...

Botflies in Cats: Signs, Causes & Care (Vet Verified)

A botfly larva doesn’t intend to find its way onto your cat, but it could cause a problem if it does. Once there,...

Healthy Paws Pet Insurance Review in 2025: Pros, Cons & Verdict

Healthy Paws Pet Insurance is a company with policies underwritten by Chubb companies and is licensed in all 50 US states. Its pet...

20 Interesting & Unique Bengal Cat Facts (2025 Update)

Bengal cats are often sought after for their wild and unique beauty. However, many people underestimate the needs of these felines. A Bengal...

Keep reading

10 Best Cat Foods in the UK of 2025 – Reviews & Top Picks

Choosing the right cat food for your furry friend is one of the most important decisions that you can make when it comes to their health and welfare. While it might not matter what color collar your cat wears or...

Calico cat eating

8 Best Cat Foods to Prevent Vomiting in 2025 – Reviews & Top Picks

One of the most frustrating things for a cat owner is when their cat is frequently vomiting. It will often be something simple like a hairball or a recent change in food and should pass quickly, but if it turns...

tabby cat eating from metal bowl

Cat Ear Language: What Feline Body Language Can Tell You (With Examples)

If you’ve ever spent any time observing your cat’s ears, you’ll already know that you can detect your cat’s feelings by how their ears are positioned. Cats can express many emotions and different moods through their ears, and when taken...

close up ragamuffin beside the window

Can Bird Mites Live on Cats? Vet-Verified Facts & Tips

Bird mites are parasites that feed on the blood of avian hosts. While they can’t survive off of feline blood alone, they can still cause irritation for cats for a couple of weeks. So, it’s best to address the issue...

Cat wearing collar scratching and itching

Detox for Cats: Vet-Verified Facts & FAQ

You’ve likely heard about many types of detox programs out there for people. It seems like there’s one for every lifestyle and budget. In fact, detoxing has spilled over into the pet world! But can cats benefit from a detox?...

cat and owner and vet

Why Does My Cat Hunt? Vet-Approved Behavior Science & Information

If you make sure your cat is always well-fed and has plenty of toys, it can be frustrating to find that they still want to hunt. Whether that’s catching something in your backyard or stalking the dog, most cats can’t...

Black Oriental Shorthair in the grass

Can Cats Eat Salmon Skin? Vet Reviewed Facts & Health Guidelines 

Salmon is an all-time favorite treat for many cats thanks to its tantalizing aroma, but can cats eat salmon skin? As long as the salmon is thoroughly cooked (plain, not with seasonings) and your cat doesn’t have a sensitive stomach,...

Can Cats Eat Salmon Skin

Can Cats Tell What a Human Baby Is? Vet-Verified Information

Cats are peculiar creatures; some are curious and friendly and want to be near you, while others retreat to their favorite lounging spot with no desire to be bothered. Some cats tolerate noise, while others hate the sound of screaming...

cat with a sleeping baby