How to Introduce Cats

Cats are territorial, and a strange cat appearing in their home is one of the most stressful things that can happen to them. Put two cats together on the first day and you’ll often get hissing, chasing and hiding, and a bad first meeting can leave them wary of each other for months. Cats Protection warns that rushing an introduction can lead to long-term conflict.

The good news is that a slow introduction works for most cats. The idea is to let them get used to each other’s smell first, then the sight of each other, and only then share a room, moving on to the next step only when both cats are relaxed. Here’s the process:

1. Give the newcomer a room of its own, with everything it needs, for at least a few days.
2. Swap scents with bedding or a cloth until both cats ignore the other’s smell.
3. Feed and play on either side of a closed door.
4. Let them see each other through a tall gate or a door opened a crack, for a few minutes at a time.
5. Hold short, supervised meetings in the same room, with a wand toy and treats.
6. Build up the time together, and only leave them alone once every meeting goes calmly.

Before You Bring a New Cat Home

Get the newcomer checked by a vet. Cornell’s Feline Health Center advises keeping a new cat apart from your other cats until a vet has examined it, and testing it for feline leukemia virus (FeLV) and FIV. Make sure vaccinations and parasite treatment are up to date for every cat, and that both are neutered, which Cats Protection recommends before an introduction.

Think about who you’re introducing. Cats with similar ages and energy levels usually get along best. A young, playful kitten can be a lot for a quiet senior cat, and Cornell notes that a new pet can be hard on an older cat. Littermates, or an adult pair that already lives together, settle most easily. If you’re adopting from a rescue or a cat café, ask how the cat has got on with other cats.

Set up enough of everything. The most common cause of tension between cats sharing a home is having to share too few resources, according to the Feline Veterinary Medical Association’s guide to introducing a new cat. The usual rule is one per cat plus one: for two cats, three litter boxes, and at least two places to eat, to drink, to scratch and to rest up high, spread around the home so that one cat can’t guard them all. Our guides to the best litter boxes and best cat trees can help.

Step 1: Give the Newcomer a Room of Its Own

Choose a room your resident cat doesn’t use much, such as a spare bedroom or a home office, and set it up as the new cat’s base: a litter box, food and water, a bed, a scratching post, a few toys and a place to hide. Bring the new cat home in a carrier, put the carrier in that room, and let it come out in its own time.

Keep the door shut. The new cat gets to settle in one small, safe space, and your resident cat keeps the rest of its home unchanged. Spend time with both cats every day, so neither feels left out.

How long does this take? International Cat Care says the newcomer may need several days to a week or two to settle, and Cats Protection suggests at least a week. Move on when the new cat is eating, using its litter box and exploring the room rather than hiding most of the time.

Step 2: Swap Scents

Cats recognize each other mostly by smell, so this is the step that matters most. Cats Protection calls it the most important stage of the whole introduction.

• Swap bedding. Put a blanket or bed the new cat has slept on in the resident cat’s favourite area, and vice versa.
• Use a cloth. Gently rub a clean cloth or sock on one cat’s cheeks and forehead, where its scent glands are, and leave it on the floor where the other cat spends time. Cats Protection suggests giving a treat if the cat sniffs it and then walks away calmly, and topping up the scent every day.
• Swap rooms. Once both cats are calm about the scents, let the new cat explore the rest of the home for a while each day, with the resident cat shut in another room, so each can investigate the other’s smell everywhere.

Keep going until both cats sniff the other’s scent and ignore it. If one hisses at the cloth or avoids it, give it more time.

Step 3: Feed and Play on Either Side of the Door

Next, link the other cat’s presence with good things. Feed both cats at the same time, with the door between them closed and the bowls a few feet from it on each side. Over the following days, move the bowls a little closer to the door as long as both cats keep eating calmly. Best Friends Animal Society suggests moving the bowls closer gradually, and backing off if either cat stops eating.

Play works too. The Feline Veterinary Medical Association suggests short play sessions with a toy on each side of the door, so the cats hear each other having fun and may even reach under the door to bat at the same toy.

Step 4: Let Them See Each Other

Once they’re both calm at the door, it’s time for the first look. Keep these sessions short: Cats Protection suggests just 5 to 10 minutes at first, with treats or a game, building up slowly.

The simplest way is to open the door a couple of inches, held with a doorstop so neither cat can push it wider. A gate in the doorway is better, because the cats can see each other properly while you stay in control. Most adult cats can jump an ordinary baby gate, so pick a tall one. The COMOMY Extra Tall Pet Gate stands 55 inches (1.4 m) tall, and with its three extension panels, 71 inches (1.8 m), which is high enough to stop most cats going over. It’s held in place by pressure, so there’s no drilling, and fits doorways from 29.5 to 40.6 inches (75 to 103 cm) wide. You walk through it on a door that locks with a lift and a pull. Keep its small pet door locked during introductions, and if you’re introducing a very small kitten, check it can’t squeeze between the bars, which are 1.37 inches (3.5 cm) apart.

Humane World for Animals suggests hanging a sheet over the gate and lifting it for a moment while you toss each cat a treat, then lowering it again, a few times a day. Over time, leave it up for longer. The goal is for both cats to see each other and carry on eating or playing.

Step 5: Hold Short, Supervised Meetings

When both cats are relaxed at the gate, let them share a room for a few minutes. Pick a big room, open the gate or door, and let them come together at their own pace. Don’t carry one cat to the other.

Play is the best way to keep a first meeting calm. A wand toy keeps each cat busy at a distance, and ideally two people each play with one cat at opposite ends of the room. Da Bird is a simple classic: its feathers spin on a swivel at the end of a 36-inch (91 cm) rod, so it flutters like a real bird and keeps even a nervous cat’s attention on the toy rather than the other cat. Toss treats to both cats for calm behaviour, and keep your own voice and movements relaxed.

End each meeting while it’s still going well, before anyone hisses. Then gradually make the meetings longer.

Step 6: Build Up to Time Together

Keep meetings supervised until they’re consistently calm. Humane World for Animals suggests leaving cats together unsupervised only after several days, or even weeks, of relaxed meetings. Until then, separate them when you go out or go to bed. Keep the new cat’s room as a retreat it can go back to, and keep every resource in more than one place.

How Long Does It Take?

Longer than most people expect. Some cats accept each other within a week or two, but the Feline Veterinary Medical Association says introductions take anywhere from a few days to a few months, and sometimes longer. The cats set the pace, not the calendar. If you go back a step because things got tense, that’s part of the process, not a failure.

Signs It’s Going Well, and Signs to Slow Down

Good signs:

• Both cats eat, play and use their litter boxes normally.
• They ignore each other, or watch each other calmly.
• They touch noses, reach under the gate to play, or rub against things near each other.
• Later on, they sleep near each other, groom each other or rub against each other.

Signs to go back a step:

• Hissing or growling that keeps happening. An occasional hiss is normal at first.
• A swishing or twitching tail, flattened ears, raised fur, dilated pupils or hard staring.
• One cat hiding all the time, or blocking the other from food, litter boxes or doorways.
• Not eating, peeing or spraying outside the litter box, or pacing.

If one cat stops eating, or stays stressed for more than a few days, call your vet.

Introducing a Kitten to an Adult Cat

Adult cats often accept a kitten more readily than another adult, because a kitten is less of a threat. The steps are the same, but a kitten’s energy can be a lot for an older cat. Cats Protection suggests tiring the kitten out with play before the cats meet, and making sure the adult has high places to escape to where the kitten can’t follow. Window perches and tall cat trees work well for this.

If your resident cat is elderly or unwell, think carefully before adding a kitten. Cornell’s Feline Health Center notes that a new pet can be stressful for senior cats.

If They Fight

Most introductions involve some hissing, but if the cats start to fight:

• Never use your hands to separate them. You’re very likely to be badly scratched or bitten.
• Interrupt from a distance with a loud clap or by dropping something noisy.
• Put something between them, such as a cushion, a thick towel or a piece of cardboard.
• Separate them once they’ve broken apart, and let them calm down in different rooms.

Then go back to an earlier step, such as scent swapping or the gate, and move more slowly. If the cats keep fighting, see your vet first to rule out pain or illness, then ask about a qualified cat behaviourist.

Do Pheromone Diffusers Help?

Plug-in diffusers like FELIWAY MultiCat release a synthetic copy of a pheromone that mother cats produce while nursing, and are sold to reduce tension between cats. The evidence that they work is weak:

• A 2010 systematic review of pheromone products for pets found insufficient evidence of an effect in most of the studies it looked at.
• The main trial of this pheromone for fighting between cats, a 2019 pilot study of 45 homes, found that aggression fell in homes with the real diffuser and with a placebo. The difference between the two was small and only reached statistical significance at the last check, after six weeks. It was funded by the maker.
• A 2022 review of feline pheromone studies called the results inconsistent, and the evidence weak at best.

The 2024 feline vet guidelines on tension between cats still list pheromones as an option that may help, while noting the effect is subtle and easily overridden. Our view: a diffuser is safe and can’t hurt, so if you want to try one, plug it in the room where the cats will meet a day or two beforehand. But it won’t make up for rushing. Separate rooms, scent swapping and short meetings matter far more.

Reintroducing Cats That Already Live Together

Cats that have lived together happily can still fall out after one comes back from the vet or a stay away, because it smells strange to the other. International Cat Care suggests keeping them apart for a few hours or a day or two, washing the carrier bedding, and giving the returning cat bedding both cats have used, so it picks up the household smell again. Watch the first meeting. If they still don’t get along, go through the full introduction again, more quickly if they settle.

Introducing Cats in Short

Start the new cat in a room of its own, and swap bedding and scent cloths until both cats ignore the other’s smell. Feed and play on either side of the door, then let them see each other through a tall gate for a few minutes at a time. Move to short, supervised meetings with toys and treats, end each one on a good note, and go back a step at the first sign of trouble. Give them one of everything per cat plus one, and expect it to take weeks, sometimes months. If you’re still getting ready for your new cat, see our checklist of everything you need before adopting a cat, and our guide to the best cat carriers for the journey home.