To introduce a new cat to your cat, keep them in separate rooms first, let them get used to each other's smell, then let them see each other through a barrier, and only then allow short supervised meetings. The AAFP, ASPCA, Cats Protection, RSPCA and VCA all describe this same order: scent, then sight, then contact.
One rule runs through every stage: move on only when both cats are calm where they are. The AAFP warns that pushing ahead before each cat is comfortable can leave long-term tension between them. Cats set the pace, so the whole process can take a few days or several months.
How do you introduce cats step by step?
Before the new cat arrives: a vet check and a room of its own
The AAFP advises that every cat in the home has a recent vet check and that the new cat is tested for common contagious diseases before the cats meet. Set up a quiet room that closes securely, with its own litter box, food, water, bed, scratching post and hiding places.
Bring the new cat home in a carrier covered with a towel, so the cats cannot see each other, and take it straight to its room (AAFP). The ASPCA suggests shutting the resident cat in another room while you do this, and keeping its usual routine, feeding times and litter box spots unchanged.
Stage 1: separate rooms until the new cat settles
Keep the cats fully apart at first. VCA suggests the new cat stays in its safe room for a few days, and the AAFP says to wait until it no longer hides all the time and explores the room with confidence. Visit each cat on its own, and keep the resident cat's day as normal as possible.
Stage 2: swap scents before they ever meet
Swap bedding or toys between the cats, or wipe a soft cloth around one cat's cheeks and give it to the other. Cats Protection suggests putting the cloth in the middle of the floor so the cat can sniff it or ignore it. The RSPCA advises collecting scent only when a cat is relaxed, since a stressed cat's scent carries that stress.
Build good feelings around the door between them. The ASPCA suggests treats near the door and play with toys either side of it, and the AAFP suggests short play sessions of 5 to 20 minutes through the closed door. Once the new cat is eating, using its box and exploring, let the cats swap rooms for a while so each can investigate the other's smell (ASPCA, VCA).
Stage 3: let them see each other through a barrier
Move to sight only when neither cat hisses or growls at the door and both are eating and using their boxes (ASPCA, RSPCA). Use a tall pet gate, a screen or glass door, or a door opened a crack. The ASPCA warns that a cat can easily jump even a tall gate, so check it first.
Keep these sessions to a few minutes and end them while both cats are still relaxed (ASPCA). Feeding or playing near the barrier helps, and VCA suggests moving the bowls or toys a little closer each session. Between sessions, the cats stay completely apart.
Stage 4: short supervised time in the same room
Once both cats are completely relaxed at the barrier, play with each one, feed them, then take the barrier away for a few minutes, the ASPCA advises. Lengthen the time over several sessions. Make sure each cat has a way out and a high place to retreat to (Cats Protection).
Keep a large towel, cushion or piece of cardboard within reach to block their view if tension starts (AAFP). The AAFP and Cornell Feline Health Center also describe keeping the cats on harnesses or one in a partly covered carrier for the first meetings, at a distance, and moving them closer over several days.
Stage 5: time together without you, a little at a time
After several calm supervised meetings, start leaving the cats together for short spells and lengthen them gradually (VCA). The RSPCA suggests giving free access for a few minutes as often as possible, and extending it when the cats play, groom each other or rub against each other. Keep the new cat's room available as a retreat.
Reading each session: carry on, slow down or stop
| What you see | What it usually means | What to do next |
|---|---|---|
| Both cats eat, use their boxes and stay relaxed near the barrier | They are coping with this stage | Move to the next stage when both cats are like this (ASPCA, AAFP) |
| Playing, grooming each other or rubbing against each other | Friendly behavior | Give them longer together (RSPCA) |
| Hissing or growling at the door or barrier | A cat is not ready for this stage yet | End the session without scolding, and go back to the last stage that went well (AAFP, VCA) |
| Staring, tail flicking, or one cat blocking a doorway or the litter box | Tension that can tip into a fight | Break eye contact with a towel or cushion and distract them with play (AAFP, RSPCA, Cats Protection) |
| A cat stops eating, stops using its box or pees outside it | The cat is stressed | Go back a stage and watch closely; call your vet if it carries on (ASPCA, VCA) |
| One cat hides most of the time, or one keeps chasing and bullying the other | Ongoing conflict that tends to get harder to fix | Get help from your vet or a certified cat behavior professional (ASPCA, VCA) |
How long does it take to introduce two cats?
Introducing two cats takes anywhere from a few days to several months. The AAFP says a few days to a few months and sometimes longer, the RSPCA says a week to several months, and Cornell Feline Health Center says weeks to months for cats that show territorial aggression. Each cat's comfort decides when to move on.
Cats Protection puts it plainly: there is no way of knowing how long a resident cat will take. With kittens the gaps between stages may be much shorter, it adds, while some cats decide they do not want another cat in the house at all. If a session goes badly, going back a stage for a few days is a normal part of the process.
What each source recommends
| Source | How long it can take | Before they see each other | First meetings |
|---|---|---|---|
| AAFP (Cat Friendly Homes) | A few days to a few months, sometimes longer | Vet checks for all cats, a secure transition room, swapped bedding, then scent rubbed on each cat's cheeks, then play through a closed door | Short sessions through a tall gate or screen, then supervised time on harnesses or with one cat in a partly covered carrier |
| ASPCA | Can take a long time; patience matters most | Separate rooms, treats by the door, a towel rubbed on each cat's head and cheeks, then swapping rooms | A few minutes at a baby gate or a door opened slightly, ending while both are relaxed, then a few minutes together with the barrier removed |
| Cats Protection | Could take weeks | A sanctuary room and a cheek-scent cloth left on the floor | Through glass, then a mesh barrier, then short meetings with treats, toys and an escape route |
| RSPCA | A week to several months | Scent swapped before the cat comes home; a pheromone diffuser at least 24 hours ahead | Through a see-through or netted door or with one cat in a crate, then brief meetings in one room |
| VCA | No timeline given; no guarantee a cat will accept a newcomer | A safe room for a few days, then swapping locations for a couple of hours | A door opened partway or a baby gate, then supervised contact during meals or play |
| Cornell Feline Health Center | Weeks to months, in its advice on territorial aggression | The new cat confined to its own room; cats swapped into each other's room for about 30 minutes a day | In carriers or on harnesses at opposite ends of a room, fed there and moved closer over several days |
What each cat needs once they share the house
- One litter box per cat plus one extra, in different places rather than side by side (AAFP, ASPCA, Cats Protection)
- Separate food and water bowls, set well apart, ideally in different rooms (Cats Protection, AAFP)
- A scratching post and a bed for each cat, plus a spare (AAFP)
- Hiding places both up high and at floor level (ASPCA)
- High perches or shelves, including spots an older cat can reach and a kitten cannot (Cats Protection)
- Two separate ways in and out of the house, such as cat flaps or doors, so no cat can block another's route (Cats Protection)
- Two or more play sessions a day, at least 5 minutes each, for a high-energy cat (AAFP)
- The resident cat's usual feeding times, litter box spots and routine kept the same (ASPCA)
What if your cats still don't get along?
Cats that still fight or avoid each other after a slow introduction need a vet check first. Cornell Feline Health Center says the first step with an aggressive cat is ruling out a medical cause, and notes cats in pain may lash out at other pets. For males clashing at social maturity, Cornell advises neutering or spaying all cats involved.
After that, separate the cats and start the introduction again from the beginning, more slowly. VCA says your vet can offer behavior advice when problems are serious. Some cats never become friends, so the goal can be calm sharing rather than closeness. The RSPCA says cats that are not friendly need enough space and resources to avoid each other at all times.
Gear that helps two cats share a home
Questions about introducing cats
How long should a new cat be kept apart from my other cat?
A new cat should stay in its own room until it has settled, which VCA says usually takes a few days and the AAFP says lasts until the cat stops hiding all the time and explores with confidence. Scent swapping happens during this time, and the cats see each other only once neither hisses or growls at the door.
Is it normal for cats to hiss when they first meet?
Hissing during an introduction means a cat is not yet comfortable with that stage, and the guides cited here plan for it. The AAFP says not to scold a cat that hisses or growls, but to stop the session and give the cats more distance. VCA advises going back to the last stage that went well and trying again later.
Should I let my cats fight it out?
Cats should not be left to fight it out. VCA notes that fights make it much harder to rebuild the cats' relationship, and bites can lead to painful abscesses. Separate fighting cats with a towel or board rather than your hands, and the ASPCA advises going back to the barrier stage for about a week.
Can you introduce two cats in one day?
Two cats should not be introduced in a single day. Every introduction guide cited here describes a staged process of separate rooms, scent, sight and short meetings, and the AAFP says it can take a few days to a few months. It warns against rushing, since that can leave lasting tension between the cats.
How do I introduce a kitten to an older cat?
A kitten meets an older cat through the same stages, with a few extras. Cats Protection suggests tiring the kitten out with play, keeping the adult's routine the same, giving the adult high places the kitten cannot reach, and using barriers the kitten cannot squeeze through. Their relationship can change as the kitten matures, between 18 months and four years.
How do I introduce a new cat when I have more than one cat?
With more than one resident cat, introduce each one to the newcomer separately before letting the whole group mix, as the ASPCA advises. The ASPCA notes that different cats go at different paces, and the AAFP says not to move on until each cat is comfortable, so one pairing can be ready long before another.