How to Introduce a New Cat to Your Cat: A Step-by-Step UK Guide

Bringing home a second cat is exciting, but the moment two cats meet can make or break the whole thing. Cats aren't naturally sociable in the way dogs are, so a slow, staged introduction gives them the best chance of tolerating — and ideally liking — each other. Rush it and you risk months of tension, spraying and stand-offs.

I've introduced cats to resident cats a few times, including one very territorial older tom who did not want a kitten in his house. The method below is the one UK rescue charities use, and it's the same approach that turned that grumpy tom into a cat who eventually shared a windowsill. It takes patience, but it works.

Why introductions need to be slow

Cats are territorial and, unlike dogs, they don't have an instinctive need for company of their own kind. As the RSPCA puts it, most cats prefer to be the only cat and enjoy company on their own terms. A new cat is, from your resident cat's point of view, an intruder in a space they've already claimed.

Cats recognise members of their own social group by scent. Two cats that smell "the same" read each other as family; two cats that smell foreign read each other as rivals. The entire method below is built around one idea: let them get used to each other's smell and presence before they ever come nose to nose. Do that, and the first face-to-face meeting is far less likely to turn into a fight.

Before you start: get the set-up right

Competing over food, water or a litter tray is one of the biggest triggers for conflict, so sort the resources out first. The golden rule for multi-cat homes is one of each resource per cat, plus one spare, placed apart so a nervous cat never has to pass the other to reach something it needs.

For two cats that means:

• Three litter trays, in separate, quiet spots (the RSPCA advises one tray per cat plus a spare).
• Separate food and water stations — ideally in different rooms, and never lined up side by side.
• Several beds and hiding places, plus high perches. Vertical space lets cats share a room while keeping their distance.
• At least one scratching post per cat, so neither is forced to use "the other cat's" post.

Get all of this in place before the new cat arrives. It's much harder to add resources once tension has already started.

The step-by-step introduction

Step 1 — Set up a sanctuary room

Give the new cat one room of their own — a spare bedroom is ideal, and the quietest room in the house works best. Kit it out with everything they need: food, water, a litter tray (away from the food), a bed, a scratching post, toys and somewhere to hide. Most cats coming from a cattery or a previous home find a whole house overwhelming at first, so a single, calm room helps them settle and gives your resident cat time to adjust to the idea that something has changed.

Keep the two cats fully separated at this stage. Let the newcomer decompress for a few days before you do anything else. Your resident cat keeps the run of the rest of the house.

Step 2 — Swap their scents

This is the heart of the method. The aim is to build a shared, communal scent so each cat becomes familiar with the other before they meet.

• Take a soft cloth and gently wipe it around one cat's cheeks and forehead (where their friendly facial scent glands are). Leave that cloth in the middle of the other cat's space so they can choose to investigate or ignore it. Do the same in the other direction.
• Swap a piece of bedding between the two, so each cat rests on the other's scent. Make sure neither is left short of beds.
• Watch how each cat reacts. Relaxed sniffing, rubbing against the cloth or ignoring it are all good. If a cat hisses at, avoids or freezes near the cloth, you're moving too fast — slow right down and keep repeating this step until the reaction fades.

Stay on scent swapping for several days, or longer, until both cats are calm about the other's smell.

Step 3 — Mix scents around the home

Once the cloth swaps are going well, start swapping the cats' locations. Let the new cat explore the rest of the house while your resident cat has a spell in the sanctuary room (only if this doesn't distress either of them). This lets the newcomer learn the layout without a confrontation, and spreads each cat's scent through shared spaces so the whole house smells of both of them. Do this a few times over several days.

Step 4 — Let them see each other through a barrier

Now the cats can meet visually, but still safely separated. Use a barrier they can't get through — a glass door, a tall mesh screen, or a couple of stacked baby gates in a doorway.

• Keep the first sessions short.
• Reward calm behaviour with treats, play or a favourite meal on each side, so each cat associates seeing the other with good things.
• You want them glancing at each other and then carrying on as normal — eating, playing, dozing. Hard staring, a tense crouched body, flattened or rotating ears, growling or hissing mean it's too soon. Calmly distract the tense cat (call their name, offer a toy) and end the session on a good note.

Repeat over several days until both cats can eat and relax within sight of each other without reacting.

Step 5 — The first face-to-face meeting

Only when barrier meetings are consistently calm should you let them share a space with no barrier. Keep it brief and low-key.

• Choose a large room with escape routes and high places so either cat can retreat.
• Supervise closely, and keep the mood light with treats and toys.
• Don't restrain either cat, don't force them together, and never hold one up to the other.
• End on a positive note before either shows signs of stress. A few short, successful meetings beat one long, tense one.

Step 6 — Build up to full, unsupervised access

Gradually lengthen the shared time and reduce your supervision. If you see friendly signs — playing together, grooming each other, rubbing bodies or sleeping near one another — they're bonding, and you can let them have longer stretches together. Keep the extra resources in place permanently; even cats that get along appreciate not having to share every bowl and tray.

How long does it take?

Honestly, it varies enormously. Some easy-going cats accept each other within a week; others need a couple of months. Kittens and confident young cats tend to be quicker; older, territorial or nervous cats need more time.

| Stage | Typical time (guide only) | |---|---| | Settling into the sanctuary room | 2–7 days | | Scent swapping until calm | Several days to 2 weeks | | Room swapping / scent mixing | A few days | | Barrier introductions | Several days to 2 weeks | | Supervised face-to-face meetings | Days to weeks | | Full unsupervised access | When both are consistently relaxed |

The timeline is a guide, not a target. Go at the pace of the more anxious cat, and never skip a stage just because you're keen to see them together.

Reading the body language

Knowing what to look for is what separates a smooth introduction from a failed one.

| Good signs (keep going) | Warning signs (slow down or step back) | |---|---| | Relaxed, loose body posture | Tense, crouched or frozen body | | Ears forward and neutral | Ears flattened or rotated back | | Brief glances, then ignoring | Hard, unbroken staring | | Sniffing, then carrying on | Hissing, growling, spitting | | Eating and dozing near the barrier | Refusing to eat, hiding constantly | | Playing, grooming, rubbing (later stages) | Swatting, chasing, ambushing |

Also watch for quieter bullying once they share space: one cat blocking access to the litter tray, food or a doorway, or pouncing on the other while it sleeps. These are signs the relationship isn't settled, even if there's no open fighting.

Common mistakes to avoid

• Going too fast. The single most common error. If in doubt, spend longer on the current stage.
• Skipping scent work and going straight to a face-to-face meeting "to see how they get on". This is how fights start and first impressions sour.
• Not enough resources. Two cats sharing one litter tray or one water bowl is a recipe for conflict. Follow the one-per-cat-plus-one rule.
• Punishing hissing or growling. These are normal communication, not naughtiness. Telling a cat off adds stress and links the other cat to something negative.
• Feeding them from the same bowl too early to "make them share". Feed on opposite sides of a barrier instead.
• Giving up after one bad meeting. A tense meeting means go back a step, not that the cats will never get along.

Keeping both cats well hydrated and relaxed helps too — if your resident cat is a reluctant drinker, our guide on how to get your cat to drink more water has practical tips for setting up separate water stations.

Special situations

Introducing a kitten to an adult cat. Kittens are usually accepted more readily, but they can pester a calm older cat relentlessly. Make sure your adult has kitten-free zones and high perches to escape to, and never leave a tiny kitten alone with an adult until you're confident.

A very territorial resident cat. Expect this to take weeks and lean hard on scent work. A synthetic feline pheromone diffuser plugged into shared areas can take the edge off for some anxious cats.

Nervous newcomers going to the vet. A stressful early vet trip can knock a shy cat's confidence during introductions. If transport is tricky, our advice on getting your pet to the vet without a car may help.

When it's not working

If, after weeks of careful introductions, the cats are still fighting, one is spraying or hiding all the time, or someone is being persistently bullied, don't just push on and hope. Go back a stage, double-check every cat has plenty of separate resources, and consider help from your vet or a qualified feline behaviourist. Occasionally two individual cats simply don't want to share a home — and that's worth recognising honestly rather than forcing. In the meantime, a calm, resource-rich "parallel lives" arrangement, where the cats coexist without being best friends, is a perfectly good outcome.

Sources

• Cats Protection – Introducing cats & kittens
• RSPCA – Introducing your cat to other people and pets
• RSPCA – Litter training and litter trays for cats