Cat Aggression: Get Off On The Right Foot

It is important to get off on the right foot when introducing a new cat to your household. The first two parts of this article looked at cat aggression in multi-cat households and what you can do to help cats get along. In this last part, we will turn our attention to preventing aggression when introducing a new cat into your home. 

Getting a new cat should be an exciting time, but unfortunately, it can be stressful and challenging. This is especially true when you already have an existing cat or multiple cats in your home who might not be thrilled about welcoming a newcomer. In order to prevent problems, it is necessary to introduce the cats to each other in a friendly and appropriate way. 

This part of the article will help you get started by explaining how to introduce two cats and what warning signs when introducing cats to look out for. It will also provide some additional tips for introducing cats.

How to introduce a new cat to your home

There are five recommended steps to follow when introducing cats. These steps are also useful for reintroducing cats after a necessary separation has occurred to treat inter-cat aggression. Following these steps can prevent conflict when introducing a new cat and can help restore group harmony among cats who have not been getting along.

Step One: Create the environment and positive associations

The first step is to set up the environment for your new cat and create positive associations with this space for existing cats. During this step, the new cat is kept in a separate room with all the necessary resources. You should not allow any direct contact with the resident cats during this time. A Feliway Classic diffuser should be used. Feliway Classic replicates cat pheromones that calm cats and helps to reduce stress.

In order to create positive associations, you can hang cat toys on both sides of the door or place a bowl of treats or special food on either side of the door. Continue feeding the regular food in the normal locations.

If you are reintroducing two cats after a separation, a larger area is recommended for the confined cat. Cats that get along with the confined cat can be allowed into the area. In the case of a two-cat household, the cats should be provided with two separate areas that are roughly the same size. 

Step Two: Exchanging scents and allowing the new cat to explore

Once the cats are fairly comfortable with step one, it is time to move on to step two. Step two involves familiarizing the cats with each other’s scents by swapping the beddings. The resident cat’s bedding can be placed in the new cat’s core area and vice versa.

Next, allow the new cat to explore the home and become familiar with the environment while the resident cat is confined. The resident cat should be confined with the owner for a period of time each day in order to make it a positive experience. For example, it can take place in the owner’s bed in the evening.

If the resident cat finds the confinement to be frustrating, the length of time can be shortened, or the restricted area can be expanded. If the introduction is taking a long time because of aggression between the cats, but the new cat is otherwise relaxed, you can remove the new cat from his room and let the resident cat explore it. 

If you are reintroducing resident cats after a separation, the rooms can be swapped because both cats are already familiar with the environment.

Step Three: Allowing visual contact

You can start allowing the cats to see each other when there are no longer any signs of aggression between the cats at the door separating them. While the cats are allowed visual contact at this stage, they are still kept apart physically. Once started, visual contact sessions should be repeated as frequently as possible.

Some ways to allow visual contact while maintaining physical separation include using a transparent or netted door, opening the door a crack, or putting one or both cats in carriers or cat bags. Cat bags are designed to hold cats securely and comfortably. To make the experience positive, provide a special treat, toy, or petting as a reward.

When using carriers at the visual contact stage, it is important not to cause the cat distress. Each of the cat’s carriers should be kept in their own core area so that it is familiar to them. To give the carriers a positive association, you can put soft bedding or treats inside. Be sure that both cats are comfortable in their carriers before introducing visual contact with each other.

Giving a cat a hiding place by covering part of the carrier with a towel or blanket can help him to feel more secure. During the sessions, the carriers should be placed in the resident cat’s territory rather than in the new cat’s room. If you have multiple cats, start visual contact between just two cats at a time.

Remember to make the experience a positive one for both cats by providing treats and special toys. Keep the sessions short, and end them while the cats are still comfortable and relaxed. 

If the cats show any negative emotions, separate them immediately taking care not to become the object of redirected aggression. If the free cat acts aggressively towards the cat in the carrier, place a towel over the carrier to hide the cat.

Step Four: Supervised physical contact

You can start the next step, supervised physical contact, once the visual contact sessions are free of signs of aggression. The supervised physical contact sessions should take place frequently once started. Allow the new cat and one resident cat to be physically together for a short time in a restricted space with close supervision. You can gradually increase the length of the sessions.

Treats and toys should accompany these sessions. You can use them to distract the cats from each other if there are any signs of a negative interaction. Hiding places, tunnels, toys, and boxes should be scattered around the room. 

You should never use punishment, but if one cat shows too much excitement when approaching another, you can use a harness and leash in order to distract and redirect the cat. The cat wearing the harness should be used to wearing it and should view it in a positive way. When the cat becomes calmer, you can use the harness without a leash, and eventually, the harness can be dropped as well.

Step Five: Free unsupervised access

The fifth and final step is to allow the cats to be free and unsupervised for short periods of time. You can begin these sessions once there are no signs of aggressive behavior during the physical supervised contact and should hold them as frequently as possible. At all other times, the new cat should be in his separate room.

Start out with just a few minutes of unsupervised access. You can increase the time as long as you don’t see any aggression. It is important to create an enriched environment for cats during these sessions. Providing multiple resources and hiding places helps keep relationships positive. 

If things go well, you can make the once separate room available to all cats. If conflicts occur, the separate room can be maintained. You can allow full access to the entire space to all cats at restricted times. 

Warning signs when introducing cats

Many cat owners are excited to welcome a new cat into their home and expect their existing cats to feel the same way. They are often surprised to find that their cats don’t accept a newcomer so easily. 

In fact, aggression is very common when new cats are introduced and should be expected. Cats are more likely to get along with each other when socialized at a young age, from two to nine weeks old. Kittens are more likely to be tolerated by a group of cats than adult cats.

There are several possible explanations for aggression between resident cats and new arrivals. Lack of familiarity, perceived competition for resources, changes to the environment, and reduced space all might cause aggression to occur. Usually, it is the resident cat that shows aggression towards the new cat, but it can go the other way around.

Many cat owners who took part in a survey reported fighting when a new cat arrived. In about half the cases, the cats had been put together immediately. Most owners who reported current fighting among their cats witnessed aggressive behavior at their first meeting.

Fights between resident cats and new cats can be quite severe. Injuries to cats and to people can occur. In cases of moderate fighting, the victim might hide most of the time. This can lead to other problems, such as house soiling, diseases, or problematic behaviors caused by chronic stress.

If the new cat was added too abruptly, it will be necessary to separate the cats and restart the process. If the process began but failed because it was carried out too quickly or incorrectly, you may restart it from the point before the problems began. This might mean going back to the initial separation period.

Sometimes, aggression between resident cats and new arrivals decreases over time. In some cases, this can take a very long time or never happen. When acceptance of newcomers does not occur, rehoming may be necessary.

Summary and final thoughts

While it can be fun and exciting to welcome a new cat into your home, it is important to introduce the new cat to your existing cats carefully. Putting them together too quickly can result in fights, injuries, ongoing aggression, and chronic distress.

By following the five steps for how to introduce two cats outlined above, you will increase your chances of successful integration of the new cat into your household. The steps are also recommended in cases of separation and reintroduction of resident cats due to aggression.


Beaver, B. V. (2004). Fractious cats and feline aggression. Journal of feline medicine and surgery, 6(1), 13-18.

Ramos, D. (2019). Common feline problem behaviors: Aggression in multi-cat households. Journal of feline medicine and surgery, 21(3), 221-233.