Warning Signs When Introducing Cats & Guide To Do Successfully 

Bringing a second cat into your home can be a nerve-wracking experience for your current kitty. We give you advice on what to consider when choosing a new feline family member, an introduction timeline, and signs that the meet-and-greet isn't going as smoothly as you'd hoped.

Sally Jones

Last Updated: June 1, 2023 | 9 min read

Angry cat hisses to another cat

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Most resident cats don’t welcome a new kitty into their home with open paws. The presence of a new feline usually forces cats to go into their natural territorial mode. This can occur even with laid-back cats and those who have been previously socialized with other cats. Unfortunately, it’s just the way our finicky furballs are wired.

Your current cat will most likely see a new feline sister or brother as a threat. But you have some ways to make this huge life change an easier transition for all involved. The best things to keep in mind during this process are to take it slow, be patient, and try not to get discouraged. Cats aren’t naturally social with fellow felines, so it can take weeks and even months for them to get used to each other.

We have important tips for you to follow on everything from finding a compatible kitty to specific ways to help the introduction process go as smoothly as possible. We also share some of the warning signs when introducing cats that you may need to slow things down.

First Things First: Finding An Ideal Match

A personality match can be key when choosing a second kitty. It’s impossible to predict if the two will eventually become best buddies, but considering some of the following factors can at least help them get along better. The Animal Humane Society says that adult cats typically accept a kitten more easily than another adult cat. And American Humane says that gender, breed, size, or other qualities usually aren’t major factors to consider.

  • Try to find a cat with a similar personality and disposition to that of your resident cat.
  • If your current kitty is very laid-back, shy, or finicky about interactions, a highly energetic and boisterous adult cat may not be a good fit.
  • On the other hand, if your current cat is the wild one, a quiet, low-energy, or skittish cat may be overwhelmed in your home.

Before The Introduction

You’ll want to make sure you have everything on hand, your house set up, and a clean bill of health before bringing your newcomer home. If you adopt your new kitty from a shelter, she’s likely already been tested for feline diseases and checked for fleas, worms, and other health issues. But if your new feline friend is a stray, you’ll need to get her thoroughly checked out by your vet to protect your resident cat’s health.

What You’ll Need To Purchase

It’s important to have all of this gear for your new kitty because you’ll need to keep her separated for the first phase.

You’ll also need a tall pet safety gate or two shorter baby gates (stacked on top of each other). This keeps them physically separated but allows them to see each other. This will help the introduction process go more smoothly and is a good way to keep cats separated when you have to leave them alone.

Prepare A Separate Room

Select a small bedroom or bathroom with an inch or two of space under the door for your newcomer. Set up the litterbox, food and water bowls, toys, and bed. The space under the door will serve an important purpose with initial introductions. Being in an enclosed area of your home will help your new kitty warm up to her new environment without becoming too overwhelmed. And it keeps your cats separate so you can control the introduction process.

How To Introduce Two Cats: Step-By-Step

When introduced too quickly, two cats may take much longer to warm up to each other or, in the worst-case scenario, never get along.

Since cats are highly territorial and solitary creatures who don’t adjust well to changes in their environment, it’s extremely important to plan out first impressions. Following the steps below is key.

There’s no set-in-stone amount of time you should spend on each step. In general, many experts recommend not moving on to visual contact until at least five days. In reality, a cat introduction timeline boils down to how things are going. Just keep in mind, don’t move on to the next step until each cat seems content and is eating and using the litterbox normally. See below for positive signs and warning signs to look out for to gauge how your cats are handling each step of the process.

Step One: Bringing Your New Kitty Home

Before walking into your home with your newcomer, make sure someone else keeps your current kitty occupied, so he doesn’t see your new fuzzy bundle of joy. Take your new kitty to the room you’ve set up; this will be her temporary pad for several days. Having space under the door is key because animals use scent as a crucial way to first explore each other. This way the cats can hear and smell but can’t see or touch each other.

Step Two: Feed Them On Opposite Sides Of The Door

At mealtimes, place each cat’s bowl near their respective side of the door that separates them. Feed them at the same time. This helps them associate coming close to each other with a pleasant experience. Give both special treats near the door to enhance this positive association. You can begin to move the bowls closer to the door after each meal. You’ll continue this ritual throughout the entire introduction phase.

Step Three: Exchanging Scents

Once your newcomer seems comfortable (this could be anywhere from a few hours to a few days), it’s time to kick up the scent introductions by switching places. This method allows each cat to further sniff out the other’s scent.

  • Remove your newcomer from her pad and take her to a location where your current kitty can’t see her (no sightings are extremely important at this stage).
  • Let your resident catwalk into the pad and shut the door.
  • Then allow your new cat to explore your house.
  • Repeat this swap several times per day.

An excellent additional way to exchange scents is by rubbing your cats with the same towel or blanket separately to intermingle their scents. Then leave the towel with each cat for a while so they can investigate their intermixed scents.

During this time, you may also want to play with the cats near the door. You can encourage them to paw at a small ball or mouse toy under the door. If things go well, they could even bat the toy back and forth. This gets them to associate a positive, fun experience with each other.

Step Four: Making Visual Contact

The next step is to open the door and place a tall gate in the doorway. This way, they still don’t have full access but can see and have some contact with each other. Once you’ve secured your gate, have someone place each cat on the floor several feet from the gate at the same time. When they notice each other, give them a treat and praise to make the experience less stressful.

Expert Tip: Many cat behaviorists recommend starting the visual introduction by first draping a blanket or sheet over the gate. This method gives you more control over the degree of visual access, so you can gradually let the cats get used to the sight of each other. Anxious cats may benefit from this extra layer of taking things slow.

Continue feeding, treating, and playing with your cats near the gate, gradually moving bowls and toys closer. If all’s going well, you can even try engaging them in interactive play with a cat wand toy or a laser pointer.

Positive Signs When Introducing Cats

If your cats are exhibiting the following signs in the visual introduction phase, it’s likely time to take the next big step to the full meet-and-greet. However, many cats will only reach the point of eating near each other, so it’s fine to move on as long as there aren’t any warning signs.

  • Eating food and treats and playing with a toy close to the other cat.
  • Ignoring each other but seeming content on their side of the gate.
  • Touching noses through the gate.
  • Rubbing their bodies against the gate.
  • Pawing each other playfully through the gate.

Step Five: The Full Meeting

Once your cats seem comfortable with one another’s presence, it’s finally time to remove the barrier. Be sure to supervise their face-to-face meetings, keeping them short initially. It can help to have a family member or friend with you during the first few meetings. Start by having your resident cat already occupied with a pleasurable experience (e.d., a toy, cuddle time, etc.), and then bring in your new cat and immediately engage her. The goal at first is to keep both cats preoccupied with positive experiences so that their entire focus isn’t just on the other cat in the room.

Mild hissing or growling can be normal at first, but if there are signs of aggression or the hissing and growling escalates, redirect the cats with toys. Gradually increase their supervised time together until you’re confident they won’t start fighting.

Step Six: When You Have To Leave Them Home Alone

While you’re in the process of having your cats physically together, it can be wise to keep them physically separated when there’s no supervision possible. This step may not be necessary if your kitties are showing positive signs. But if not, keeping them separate when you’re away can help over the long term until they get used to each other.

9 Warning Signs When Introducing Cats

Couple of Ragdoll cats
Following these steps, you should have happy cohabitating cats.

Before you start your cat introductions, it’s helpful to familiarize yourself with the warning signs to look out for throughout the entire process.

  1. Intense staring at each other: A stare-down is a common way cats size each other up, but if it goes on for too long or you notice accompanying warning signs, it’s time to separate them.
  2. Dilated pupils: Wide open eyes and dilated pupils are signs that a cat is nervous and feeling defensive. It usually occurs when they first see each other.
  3. Flattening their ears: When cats’ ears are lying flat or turned backward or sideways, it means they’re feeling threatened by the other cat. Cats often flatten their ears when feeling frightened or annoyed.
  4. Puffed-up fur: Cats typically puff up their fur as a sign of dominance or fear. When two cats meet, this is a sign that one (or both) are trying to look as big as possible. The more submissive cat will usually puff up larger than the other one.
  5. Swishing tail: If your cat’s tail is twitching back and forth when in the presence of another cat, this can be a sign of agitation. Cats also swish their tails when they’re excited, so pay attention to other cues.
  6. Growling: Growling is a normal way cats communicate that they’re feeling uncomfortable in a situation. Some growling is to be expected, but if it’s prolonged, you may need to slow down your process.
  7. Hissing: Hissing is a natural way cats vocalize that they’re feeling fearful and threatened. It’s a warning sign to stay away. Hissing is extremely common when introducing cats, and it’s usually not a major concern.
  8. Stalking, chasing & hiding: The more submissive cat may slink away and hide under furniture, while the dominant kitty may try assert his power by stalking and chasing. This is a sign to slow down the process.
  9. Urinating outside the litterbox: You most likely will notice this with your resident cat. It means he’s feeling threatened by the new cat and is defending his turf by marking his territory.

Reading Cat-To-Cat Body Language (Video)

Not sure how to read your cats’ body language when they’re interacting? This video from cat behaviorist guru Jackson Galaxy is a must-see to help you understand what’s going on and what to do about it.

Frequently Asked Questions

Can’t you just put cats in a room together and let them work it out?

No. While this introduction process may seem like overkill to you (and your patience level), it’s crucial for a successful relationship. Sure, some laid-back cats may be fine with each other fairly quickly, but that’s not a chance you want to take. You never know how a cat will react. And “letting them work it out” is a potential recipe for disaster.

What if I have multiple resident cats?

Unfortunately, the best course of action is to introduce the newcomer to each of your current cats separately.

How much hissing is normal when introducing cats?

Hissing is a natural way for cats to communicate, so don’t be alarmed if one or both of your kitties exhibit this behavior. It may begin as soon as they sense each other through the closed door, but some may not hiss until the full in-person meeting.

What do I do if a fight breaks out?

Never just let cats work it out with a fight. It’s important to separate them immediately, but don’t try to physically get between them. You could end up being injured by flying claws. Stop the fight by distracting them with a loud noise or another means.

What are the signs that cats are starting to get along?

It can take many cats a good 8-10 months to become friends, and some will merely tolerate each other and never reach the friend zone. Signs cats are starting to get along include:

  • Gently head butting
  • Touching noses
  • Hanging out near each other
  • Grooming each other
  • Sleeping together
  • Play fighting and chasing

Final Thoughts

Following these steps carefully and heeding the warning signs when introducing cats can be a game changer for a successful and peaceful coexistence. This process can most certainly be a test of your patience. And don’t be discouraged if your feline family members are taking a long time to get along. Most cat behavioral experts agree that this slow approach is your best chance for a harmonious kitty home.

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