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Dog Suddenly Aggressive Towards Other Dog In the House

What should you do if one dog is being aggressive towards the other dog in your own house?

Some dogs may even attack their fellow canines, leaving owners with lots of questions.

Wondering about how to reintroduce the dogs? Should you separate them?

What’s the line you should draw when it comes to the safety of other members in the house?

And most importantly why are your dogs even fighting and how can you stop it long-term?

While it’s always saddening us to witness our beloved dogs fight each other, the problems are often pretty easy to solve if owners commit to the training.

You’ll learn why one dog may have become aggressive towards the other and how you can stop it.

But you’ll also what the signs of a serious fight are and how you go about reintroducing and separating the dogs.

8 Reasons Why Your Dog Is Suddenly Aggressive Towards Other Dog

Reasons why your dog is suddenly aggressive towards the other dog include resource guarding, food aggression, redirected overexcitement, but also medical issues that cause pain.

If you recently introduced a puppy or rescue dog, that may be the reason.

Seniors are often suffering from medical issues ranging from hip issues to doggy dementia and that may cause a short fuse or disorientation.

External changes are also reasons why your dogs may not act like themselves.

Here’s a complete list of why dogs are suddenly aggressive:

  1. Resource guarding / food aggression
  2. Redirected overexcitement
  3. Lack of exercise
  4. Desire to be left alone
  5. Jealousy
  6. Medical issues
  7. Recently neutered
  8. Territorial issues / previous aggression
White brown dog lying on the floor.
Photo by Aleksey Boyko on Shutterstock

While your dog might not outright attack the second dog in your household, signs of aggression can be a tell that something might happen in the future.

How can your dog display aggression towards your other dog?

  • Growling or snarling upon approaching
  • Baring teeth when food or toys are around
  • Snapping your other dog when overexcited
  • Redirecting leash reactivity towards other dogs
  • Bullying the weaker (usually smaller or younger) dog

These signs can all be perceived as aggression and can be indicative of future problems that might arise.

A very tense relationship is never welcome and should be resolved immediately upon being noticed, but what can you do?

My Dog Keeps Attacking My Other Dog For No Reason

Dogs never attack another dog for no reason and there’s always an underlying behavioral issue or an undetected medical issue causing pain.

While it may seem like our dogs just go into a murderous frenzy out of nowhere, that’s actually almost never the case.

Dogs always communicate using their body language which includes facial and vocal gestures like growling, body postures, and tail positions.

We humans can sometimes have a hard time reading these signs but even though threats can be pretty clear to dogs, they too can challenge their fellow canine. And sometimes both refuse to back down.

In other cases, it’s just known issues that one dog has and the other doesn’t, as is the case with food aggression.

While the aggressive dog may have initially triggered a dog fight, your other dog might as well be the first to attack. Every dog has a different threshold for what they take.

Keep in mind that it’s never your dog’s fault, some dogs just have a tendency to take less bullying than others and they might strike the provoking dog.

As a responsible dog owner, it’s your responsibility to take precautions if one of your dogs has known issues like resource guarding, food aggression, not wanting to be annoyed by your new puppy, and so on.

How To Stop Dogs From Fighting In the Same Household

You can stop dogs from fighting in the same household by addressing the underlying behavioral issue such as food aggression and counter-conditioning a positive response.

When it comes to stopping your dogs from fighting at home (or outside), it’s important to note that I’m referring to constant nagging, snapping, growling, and so on – not any immediate threat or dog attack.

I have an article that covers the actual dog on dog attack if you’re interested.

To stop dogs from fighting, the most important question is why your dogs fight in the first place.

Once you know the root of the problem, you can take care of it.

1. Food Aggression / Resource Guarding

The basic explanations for fights with dogs are always resource guarding and food aggression.

Pitbull jealous of other dog.
Photo by Tara Lynn and Co on Shutterstock

If one dog is known to have either of these issues, please take care of it early on and read the linked articles.

2. Redirected Overexcitement

If you walk your dogs outside or guests are over and one of your dogs redirects the negative energy to your other dog due to his level of excitement, training will be required.

If that is the case, it’s best to walk your dogs separately and work on the overexcitement with lots of new situations, dogs, humans, noises, etc.

The whole desensitization and socialization package.

My Rottweiler puppy was quite overexcited too (which presented as tension on the leash, nothing serious) and the causes and ways to solve this are almost always identical which is why I’ve written an article on this too.

3. Lack of Exercise

If one of your dogs lacks exercise, this could be another reason why he is constantly nagging your other dog.

Besides extensive walks, there are several other things you can do to entertain your dog in your own backyard.

Make sure to adjust the amount and kind of exercise to your dog’s breed, age, and individual needs.

Sometimes this also means walking the dogs separately as they can have different exercise needs.

A tired dog is a good dog.

4. Annoyed Dog (Puppy Alarm)

When people introduce a new puppy into the family, the adult dog might not be so happy.

Some adult dogs despise puppies while others handle them very well and can be the best teachers

If your dog just doesn’t have the temperament to deal with puppies in their face all day, that’s okay.

If one of your dogs constantly annoys the other dog, you have to keep this from happening again and teach them how to respectfully treat and measuredly correct each other in an appropriate way.

5. Jealousy

When you introduce a new rescue and he’s all the rave, neighbors come over and pet him, he gets all the attention, then that may be great for him but much to your other dog’s dislike.

Dogs can feel some form of jealousy and it’s important to teach your first dog to handle jealousy but also make sure that both get attention equally.

Go on bonding trips together and make sure they connect each other with positive things and not with negative experiences.

6. Medical Issues

Medical issues can cause one of your dogs to suddenly start attacking the other dog in the household and a vet visit is required to rule that out.

Ruling out physical injuries can be tricky, but ruling out mental issues? Even harder.

You can check simple things like foreign objects stuck in the paw yourself.

Injuries are often not discovered right away and the resulting change in mood might be perceived as aggression if there’s another dog in the household.

Older dogs often suffer from canine dementia but dogs of all ages can suffer chemical imbalances, hormone issues, and so on.

7. Spay or Neuter

If your dog was recently spayed or neutered, then hormone balancing may be the cause of your dog’s aggression towards your other dog.

Read up about the risks of spaying and weigh them against the benefits to make sure you know all about possible behavior changes upfront.

8. Territorial Issues

I’ve decided not to include “dominance” since many people immediately connect that to the outdated dominance theory in dog training.

However, if you introduce a new dog, issues can happen if the introduction to each other was poor or non-existent.

Whether you believe in pack theory or not, it’s important that your dogs listen to you and recognize you as the leader and guide in which case training will be far easier.

Dog-on-dog aggression can not only happen between males but also between females or even male and female dogs.

If your new rescue has come with baggage in form of dog aggression, you can resolve the issues with the steps and articles outlined above that include socializing and desensitizing your dog to others in order to create a positive connection.

The assistance of a behaviorist may be necessary.

Reintroducing Dogs After a Fight

Reintroducing both your dogs in the same household is an important step on the road to rehabilitation.

In some cases, poor introductions to the new family addition are the cause of the other dog’s non-acceptance.

Some dog breeds defend their territory pretty harshly since that’s what they’re bred to do.

If you’ve just dropped a new dog into the other dog’s territory, the harmony is bound to be tested.

Make sure that any and all introductions to each other happen on neutral ground. Introductions shouldn’t start with head-on meetings either since this can make one of your dogs uncomfortable.

Start by having somebody else lead the new dog towards you and then just start walking with you and your dog in the front.

Next, you can start with the meeting where they sniff each other more extensively.

Some dogs do not have any issues with dogs inside their territory (like my female Rottweiler), it’s still good to take precautions to avoid any confusion.

How To Tell If a Dog Fight Is Serious

There are a lot of signs that a dog fight is serious such as an injury (i.e. one dog was bitten), tense body language, hackles, whale eye, and more.

If a serious fight develops, it’s time to quickly intervene.

After this happened or even when you’re just suspecting it, you should never leave your dogs alone if they’re not separated (and if that’s not possible, they should wear muzzles).

Muzzles are also mandatory if your dog is known to redirect any perceived aggression towards you, or other dogs and people.

I’d never recommend to anyone that they should let any dog fight “play out by itself”.

While there certainly is a threshold when a dog attack gets really serious, you don’t want to get to that point.

As discussed above, if you spot signs of aggression, intervene and separate the dogs until you have a clear plan of what to do now and how to resolve any issues that may have built up over a long time.

How To Discipline a Dog After Fighting

While dogs do learn with proper guidance, corrections, and counter-conditioning, there’s nothing that you can immediately do that will resolve the issue.

I actually have a full article on how to discipline dogs after fighting.

There’s also an article on how to discipline your dog in general.

Keep in mind that any correction should always be clear, but measured to not achieve the reverse effect of your dog losing respect for you too.

Separating the dogs is not a long-term solution, although it will work in the short term until you’ve figured out what the problem exactly is and how you can resolve the issue.

On the contrary, constant separation will put much stress on both dogs as well as yourself and other family members in which case a harmonic life isn’t possible anymore.

If you go so far as to isolate one of the dogs, it might cause even more issues and resentment expressed as aggression than before.

My Dog Killed My Other Dog What Should I Do?

This is a question you’ll find on Reddit more often than you’d probably like to.

It’s a sad story, no matter what the circumstances were but it’s important to not stick your head in the sand and start addressing this issue.

The advice that’s spread by people that presumably never really read up about dog training and behavior can be really dangerous.

Next is the popular “just surrender that dog to a shelter” or even better “euthanize the dog”.

Nearly no shelter will take a dog that killed another animal, much less another dog.

Even if they did, they probably couldn’t train it and the dog would end up in the hands of a layman, without the slightest mention or explanation of the incident.

Euthanizing a dog for a mistake the owner made is also completely unacceptable in my personal opinion.

No matter how you look at this, falsely assessing your dog(s) and/or not taking security precautions is a mistake.

We can’t fix the past, but we can act differently in the future.

Start training with professional help.

And I don’t just mean a certified trainer, I mean a really qualified behaviorist that has a proven track record and that you trust.

Be ready to put in lots of time, effort, and money.

If this is no option for you, it’s completely understandable.

Sometimes, circumstances in life make it hard to deal with these kinds of situations but you should at the very least try to solve the issue yourself (with professional help if needed).

In case you want to surrender the dog to a shelter or another owner directly, do your research, explain everything in detail, and do not downplay anything.

A dog that has taken a life can definitely be very dangerous and should only go out muzzled and not interact with other dogs unsupervised.

To summarize this, dog on dog aggression inside your own home can be really sad to watch and if you feel helpless, remember that there is a way out to teach your beloved canines to accept each other.

Lots of problems are easy fixes with the right training and patience and if you have any questions along the way, feel free to ask them in the comments!

Disclaimer: This blog post does not substitute veterinary attention and does not intend to do so. I am not a veterinarian or pet nutritionist. If your dog shows any sign of illness, call your vet.

About Danielle

Equipped with 5+ years of expertise as a Rottweiler owner, I partner with licensed veterinarians and trainers to share research-backed and actionable advice for you and your furry friend.

Tracy Martschinske

Thursday 20th of July 2023

We have a 13 year old male Dacshund and a 4 year old female labradoodle. Our labradoodle has now aggressively attacked our other dog about 4 times now. We have had her as a puppy so we know her history. 2 times have cause bad wounds on our old little defenseless dachshund. Our labradoodle is the sweetest dog ever 95% of the time. It’s either jealousy or to be honest I don’t know. We don’t want to get rid of our Labradoodle. What do you recommend. Thank you for your help


Monday 24th of July 2023

Hi Tracy, it's impossible to diagnose the problem without seeing the dogs in-person and more info. I'd suggest finding a trainer who specializes in aggressive behavior. Since it's caused bad wounds as you stated, it's a pretty serious situation and I'd act quickly.

Paul Harmer

Friday 7th of July 2023

I bought a puppy pitbull & intrduced him to my older pitbull there both males ' my older one excepted him like a son it was amazing then as the pup reached 11 months he started pushing his luck hes now 13 months & they are now starting to have serious fights & getting worse my older one was holding back but not no more & getting seeious now ' they just had a fight & both being stand offish with each other growling but they sleep & cuddle each all the time ' one of the last fights the younger one bit older ones mouth & drew blood ' after the fight the younger one was licking his wounds they love each other but lately getting worse & i dont know what i shoukd do now ' i love my dogs so much i coukdnt handle getting rid of one

Diana Driscoll

Monday 13th of March 2023

Hi! We have a 3 year old spayed female husky and a recently neutered 11 month old GSD. These two got along GREAT when we brought him home at 8 weeks and my female husky loves other dogs and people. Over the past 30-60 days we have noticed his “over excitement” in different scenarios - people coming to the door, family members returning home, going for a walk. This over excitement has been taken out on our female where he starts to show dominance -chasing, head over her shoulder, mounting. She is not pleased in these situations but he doesn’t seem to take the hint. He also “keys” in on her when she is outside on the deck and he can see her - he usually loses his mind until I can get him redirected. We decided to have him neutered 2 weeks ago and have managed to keep them mostly separate. As he is fairly well physically healed now, they have been in each others company but it usually results in his over excitement again and I need to separate them before it gets out of hand.

… I’m so frustrated. I’ve recently started training them using “The Art of Training your Dog” by the Monks of New Skete. We are only a few lessons in and both dogs are responding well. They train separately. Is it too early to see any improvements? Am I on the right track? How do I get my happy pack back?

Thank you so much for your time!



Monday 30th of January 2023

Hi I'm adriana I have 2 adult pitbulls they have lived together for many years and I never had a problem one is male and one is female they just recently started being aggressive with each other what is causing it


Friday 3rd of February 2023

Hi Adriana, the information you provided is pretty limited and it's impossible to say what is causing the tension between your two dogs. I'd suggest you consult a professional behaviorist to have the situation looked at as it can turn south pretty quickly if you notice signs of aggression. Might also be an underlying medical issue.


Saturday 31st of December 2022

Hello. I have a question. I have two dogs that have been buddies for a while. A 3 year old lab, and a 1 year old mix.

Yesterday, my mixed pup was hit by a car and was in the hospital overnight. He is better, but still has a long road ahead of him.

Since I brought him home, my black lab is suddenly growling at him and putting his hackles up around him.

When the pup was hit by the car, his breathing almost sounded like snarling, and I’m thinking maybe the lab took it as a threat?

I don’t know what to do about this. They were best friends, and now my lab seems to hate the pup.

Any advice?


Saturday 31st of December 2022

Hi Cassie, sorry this happened to your pup, hope he'll get better soon. The fact that the change is so sudden probably means that it has to do with the accident. Miscommunication is possible and your Lab might be confused or just sense the general pain in your pup. Regarding the snarling: It usually settles if your Lab is well socialized and recognizes the body language etc.

If you're worried, please don't hesitate to consult a certified behaviorist in your area, looking at it in person would be much more helpful.

Hope that helps, Danielle