How to Introduce a Kitten to an Older Cat: A Behaviourist’s Method

Almost everybody gets this wrong in the same way, and it is an understandable mistake: you have waited months for this kitten, you get it home, and you want the two cats to meet. So you put the carrier down in the living room and open the door.

That single decision causes more of the introductions that go badly than anything else. I am a GCCF judge, but I am also certified in feline behaviour and psychology and in cat anxiety and stress, and this is the question I am asked more than any other by people who have bought a kitten, usually a few days after they needed the answer. So here is the method properly, in order, with the timings I would actually give you.

Why it goes wrong, and why it is almost never a personality clash

When an introduction fails, the owner nearly always tells me the two cats “just don’t like each other”. That is very rarely what has happened.

Cats are territorial in a way dogs are not. A resident cat has spent years building a map of your house — where it is safe to sleep, which routes are hers, where the food is, where she can get up high if something frightens her. A kitten arriving is not a new friend. It is an unfamiliar animal appearing in the middle of that map, all at once, smelling wrong.

The reaction you see (hissing, growling, fleeing under the bed) is not a verdict on the kitten’s character. It is a cat responding to a territorial breach. And that matters enormously, because it means the problem is fixable by controlling how much of the map changes at once. Which is exactly what the method below does.

The other thing worth knowing: cats recognise each other primarily by smell, not by sight. Two cats that have swapped scent for a week before they ever see one another are, in a real sense, already acquainted. That is the whole trick, and almost nobody does it.

Before the kitten arrives: build the base camp

Set this up before collection day, not on the evening you get home with a kitten in a carrier and a resident cat watching from the stairs.

Choose one room the kitten can have entirely to itself for the first week or so. A spare bedroom is ideal. It needs:

• A litter tray, well away from the food. Cats do not eat next to their toilet and will hold on rather than do so.
• Food and water, in separate places from each other.
• At least two places to hide — a cardboard box on its side is as good as anything you can buy.
• Something to get up on. Height is how a cat feels safe. A chair by the window will do.
• A scratching post, so scratching starts on the right thing from day one.
• A blanket or old jumper of yours, so the room smells of you rather than of nothing.

Across the rest of the house, apply the n+1 rule before the kitten comes: one litter tray per cat, plus one spare, in different rooms. Same for food bowls and water. Most “the older cat has started weeing on the rug” problems that appear a fortnight after a kitten arrives are resource problems, not spite. I have written a whole book about inappropriate urination and this is one of its most common causes. There is a general kitten-proofing guide and a what-you-actually-need checklist on CattyLicious, the owners’ site I write.

Days one to three: scent before sight

The kitten goes straight into its room and stays there. The two cats do not see each other at all. This feels unnatural and slightly cruel, and it is neither — a kitten that has just left its mother and littermates finds one quiet room far easier than a whole strange house.

What you are doing in these three days is introducing them by smell:

• Swap bedding. Put the kitten’s blanket where the resident cat sleeps, and vice versa. Do it daily.
• Scent cloths. Take a soft cloth and stroke it gently around one cat’s cheeks and chin (where the scent glands are) then leave it in the other cat’s space. Repeat with a second cloth the other way round.
• Swap rooms, not cats. Once a day, shut the resident cat somewhere comfortable and let the kitten explore the rest of the house alone for twenty minutes. It learns the map without a confrontation, and leaves its scent as it goes.
• Feed either side of the closed door. Start with the bowls a good distance back. Each meal, move them a few inches closer. You are teaching both cats that the other one’s smell predicts something good.

If either cat stops eating, or eats only when the other’s bowl is moved back, you have gone too fast. Move it back and stay there for a couple of days. Nothing is lost by being slow.

Days three to seven: seeing without touching

Only when both cats are eating calmly either side of the door do you let them see one another, and still not touch.

The easiest way is a tall baby gate in the doorway, or the door wedged open two inches on a doorstop. Keep the first look to a minute or two, with something good happening at the same time: a meal, or a wand toy for each cat, played by two people if you can manage it.

Then close the door while it is still going well. That is the part people find hardest. You want to end every session before either cat has had enough, so that the next one starts from a good memory rather than a bad one. Build up over several days from a minute to ten.

The first proper meeting

Usually somewhere in the second week, though let the cats set the pace rather than the calendar.

• Pick a big room with escape routes, and make sure there is high furniture the older cat can retreat to. Never do the first meeting in a corridor or a small bathroom.
• Leave the kitten’s door open so it can bolt back to its own territory.
• Do something else. Feed them both, or play. Two cats occupied with a toy are not studying each other.
• Do not pick either cat up to “show” it the other. It removes their ability to leave, which is the one thing keeping them calm.
• Do not shut them in together and let them sort it out. They will not. What they will do is form a bad association that takes months to undo.
• Ten minutes, then separate, on a good note. Repeat daily, extending gradually.

Do not leave them alone together unsupervised until you have had a couple of weeks of calm, boring meetings. Boring is the goal. Boring is what success looks like.

Normal friction, and the signs that mean stop

People panic at the first hiss and undo three weeks of careful work. Some friction is not only normal, it is the two cats negotiating, which is what you want them to do.

Normal, keep going:

• Hissing or a short growl, then walking away.
• The older cat swatting a kitten that has bounced on her. That is a correction, and kittens need them.
• Staring, then losing interest.
• Keeping to opposite ends of the room for a fortnight.

Slow down or go back a stage:

• Either cat stops eating, or eats only when the other is shut away.
• The older cat stops using the litter tray, or starts toileting elsewhere.
• Sustained growling, flattened ears and a low crouch, not a moment, but a state she stays in.
• One cat blocking access to the tray, the food or the door. This is quiet bullying and it is easily missed.
• The older cat stops coming downstairs, or disappears for most of the day.
• Any fight that draws blood, or a chase that ends with a cat cornered.

None of those mean it has failed. They mean the last step was too big. Go back to the previous stage, stay there twice as long, and build up again more slowly. If the older cat’s toileting changes, get her checked by your vet before you assume it is behavioural — stress and illness look identical from the outside, and cats hide pain well.

The mistakes I see most

Doing it all on day one is by far the commonest, and the hardest to recover from, because the resident cat’s first memory of the kitten is fright. Close behind it is telling the older cat off for hissing, which adds your disapproval to an already stressful situation and teaches her that the kitten’s presence predicts trouble from you as well.

Then there is making a fuss of the kitten in front of her. Greet and feed the resident cat first, every time, for the first month. It costs nothing and it matters more than almost anything else here.

One litter tray is the single most reliable way to create a toileting problem in a two-cat house. It is the subject of my book Stop Cats Peeing, and I can tell you that a chapter of it could have been avoided entirely by buying a second tray.

And giving up at three weeks. Plenty of pairs that now sleep curled round each other took two months to get there.

How long it actually takes

Honestly: expect two to six weeks to reach comfortable coexistence, and longer for genuine friendship if it comes at all. Some cats become inseparable. Some settle into polite indifference and share a house perfectly well for a decade. Indifference is a good outcome and you should not feel short-changed by it.

Age matters. A kitten going in with a cat of one or two usually settles quickly — the resident is still playful enough to engage. An older cat, say ten or more, needs longer and needs you to protect her space more firmly: somewhere high, or a room behind a baby gate, that the kitten simply cannot reach. Arthritic cats in particular need an escape route that does not involve jumping.

Temperament matters too, which is worth thinking about before you choose. British Shorthairs are, as a rule, phlegmatic (they tend to absorb an upheaval rather than react to it) and that makes them easier than most breeds to introduce in both directions. There is more on what the breed is actually like on the temperament guide on the breed site I write.

What we do here, and why it makes your job easier

Everything above is easier if the kitten arrives already knowing that other cats exist and are not a threat. That is not luck, it is how the kitten is reared, and it is worth asking any breeder about.

Our kittens are not raised in a cattery block. They grow up underfoot in the house, among adult cats and ordinary household noise — the vacuum, the doorbell, the television. We also breed Siamese and Orientals under the Burnthwaites prefix, so a British Shorthair kitten from us has spent its first fourteen to sixteen weeks living alongside cats with a completely different temperament from its own. The photograph above is Rosie with one of the Orientals, and that arrangement took weeks of exactly the process described on this page.

A kitten that has already negotiated space with an adult cat that is not its mother has done this before. It will read your cat’s signals, back off when told, and not take a swat personally. That does not make the introduction unnecessary (do every step anyway) but it stacks the odds considerably in your favour.

And if you hit a problem after your kitten comes home, ring us. Behaviour questions are the part of this I enjoy most, and we would always rather you called early than worried alone.

Frequently asked questions

How long does it take to introduce a kitten to an older cat?

Two to six weeks to reach comfortable coexistence is normal. Older or more nervous cats take longer. Rushing it is the one thing that reliably makes it take longer still.

Should I let them meet straight away?

No. Keep the kitten in one room for the first few days and introduce them by scent first — swapped bedding, scent cloths, and feeding either side of a closed door. Cats recognise each other by smell, so this is a real introduction, not a delay.

My older cat is hissing at the kitten. Is that a problem?

Usually not. A hiss or short growl followed by walking away is normal negotiation, and a swat at a kitten that has pounced on her is a fair correction. Worry about sustained growling, a cat that stops eating or using the tray, hiding all day, or any fight that draws blood.

How many litter trays do I need for two cats?

Three — one per cat plus a spare, in different rooms. Sharing a single tray is one of the most common causes of a resident cat starting to toilet elsewhere after a kitten arrives.

Should I let them fight it out?

Never. Cats do not resolve territorial disputes by fighting the way people imagine. They form lasting negative associations instead. Separate them calmly, without shouting or grabbing, and go back a stage.

Is it easier to introduce a kitten than an adult cat?

Generally yes. A kitten is not yet a territorial rival and most adult cats tolerate one more readily than another adult. It still needs the full process — the resident cat’s experience of the upheaval is the same either way.

Will a second cat help if my cat is lonely?

Sometimes, but do not assume it. Plenty of cats prefer to be the only one, and a companion added for the owner’s benefit rather than the cat’s can make things worse. If your cat is content alone, that is a reason to think carefully rather than a problem to solve.

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If your resident cat is the reason you have been putting this off, say so when you enquire. It is the most useful thing you can tell a breeder, and it changes which kitten I would put you with — a bold kitten going to a nervous older cat is a very different proposition from the other way round. Tell me about your cat before you start thinking about kittens.