How to Introduce a New Cat to Your Cat: A Step-by-Step Plan
LitterBond Team
By the LitterBond Team · Researched against FelineVMA (AAFP), Cornell Feline Health Center and iCatCare guidance · Last updated: November 3, 2026
The new cat came home last weekend. She's in a carrier by the door, making small, worried sounds. Your cat of six years sits on the stairs with a puffed tail, staring. You hoped they'd be friends by the holidays. Your cat has other plans.
Here's how to introduce a new cat to your cat: slowly, and at their pace. They meet by scent first, then by sight, then in short visits you watch. The Feline Veterinary Medical Association (FelineVMA, once called the AAFP) is clear about the timeline. It says the process can take "anywhere from a few days to a few months, and sometimes longer."
Below is the plan, one step at a time. You'll also learn which hisses are normal, and when to call your vet.
Get Ready Before Day One
Most of the work happens before the cats meet. You need a vet visit, a room for her and some patience.
Book a Vet Check First
Your new cat should see a vet before she shares the house. The Cornell Feline Health Center says any new cat "should be checked by a veterinarian as soon as possible" once she's home. If her past is unknown, Cornell advises tests for two viruses. They are feline leukemia virus (FeLV) and feline immunodeficiency virus (FIV). Your vet will also check her for worms inside and fleas or ticks outside.
Until then, keep the two cats apart. Cornell says to keep a newcomer away from your other cats until your vet has seen her. The FelineVMA guide adds that all your cats should have had a recent checkup too.
Set Up a Base Room
Your new cat needs a room of her own for the first days. Pick a quiet room your first cat doesn't use much. International Cat Care (iCatCare) lists what goes inside:
✅ Base room checklist (iCatCare)
- Food and water bowls
- A litter box
- A soft bed or two
- Hiding spots, like a box on its side
- A few toys
- A scratching post
iCatCare says these should be the new cat's own things or brand new. Don't borrow them from your other cat.
Then give her time to settle in. iCatCare says it depends on the cat, from "several days to a week or two." She's ready when she eats, plays and uses the box as normal. Rubbing her face on the furniture is a good sign too.
Plug In a Diffuser Early
A plug-in pheromone diffuser is one extra tool for this stage. The FelineVMA guide suggests one in the main living area and one in the new cat's room. It says to plug them in "24–48 hours before the new cat arrives."
The guide didn't test or review LitterBond's diffuser. If you want to try one, the Calming Diffuser Kit (1 diffuser + 2 refills) suits the main living area, and the 2-Room Kit also covers the new cat's room. It's a drug-free plug-in that people can't smell. It runs day and night. The two 48 ml refills give about 60 days of nonstop use in one room. That fits the slow pace below. It helps many cats feel more at ease, but it can't do the work for you.
Will your cats live in two rooms, far apart, for a while? The Calming Diffuser 2-Room Kit (2 diffusers + 4 refills) covers both rooms. Plug each one in where a cat spends the most time. Never cover a diffuser while it's plugged in.
Calming
One diffuser, two refills, about 60 days
One plug-in diffuser and two 48 ml refills: about 60 days of nonstop use in one room. It's drug-free and people can't smell it. It helps many cats feel more at ease. It can't replace the slow steps, or separate bowls and boxes for each cat.
See the diffuser kit →Start With Scent, Not Sight
Cats get to know each other by smell first. So this step happens with a closed door between them. Wondering how to introduce cats to each other without a fight? Start here, and don't rush it.
Try these three ways to share scent:
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1
Swap bedding
iCatCare suggests letting each cat lie on the other's blanket. Over time, the two smells mix into one shared smell.
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2
Share a cheek rub
Best Friends Animal Society suggests towels "gently rubbed on the other cats' cheeks." Rub a soft cloth on one cat's cheeks. Then leave it near the other cat.
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3
Swap rooms
Close your first cat in a room for a short time. Let the new cat explore the house. VCA Animal Hospitals suggests a couple of hours. Then each cat goes back to its own space.
iCatCare adds one caution about room swaps. Only close your first cat in a room if it won't upset her.
Watch how each cat reacts to the other's smell. Sniffing and walking away is a good sign. Hissing at the blanket means you slow down. The FelineVMA guide sets one rule for every step. "Do not move to the next step until each cat is comfortable with the current step," it says.
Feed Them on Either Side of a Door
Meals help each cat link the other's smell with something good. Best Friends suggests feeding them on either side of a closed door. Start with the bowls several feet from the door. Then move them a little closer as the cats relax.
Play works the same way. The FelineVMA guide suggests play on each side of a closed door. It says to keep sessions short, 5 to 20 minutes. Stop before the cats lose interest. A toy on a string under the door gap is plenty.
Not every group agrees on food here. iCatCare advises against using food or play "to distract or reward your cat" during this process. So never use a meal to push a cat closer than she wants to go. If either cat won't eat near the door, move the bowls back.
Let Them See Each Other
Once smells are old news, let them look. Keep a barrier between them at first. Any of these works:
- A cracked door. Best Friends suggests a door "propped open a couple inches."
- A tall baby gate. Humane World for Animals suggests a tall, sturdy gate, at least 36 inches high.
- A screen or glass door. iCatCare lists these, along with a door left ajar.
Keep the first looks short, and keep both cats busy. VCA suggests giving each cat food or a toy. Then slide the bowls or toys closer to the barrier during each session.
If one cat hisses or growls, don't scold her. The FelineVMA guide says to "stop the interaction and distance the cats." Try again later, from a little farther back.
Keep Early Visits Short
The first time in one room should be brief, calm and watched. iCatCare suggests opening the barrier when the cats are busy with something else. VCA says to stay close. That way you can separate them if either one looks upset.
End each visit while it's still going well. Humane World for Animals says to end "on a positive note (before there are any signs of stress)." A few calm minutes beat an hour that ends in a swat. Add a little time each day.
The first time you leave them alone together, keep it short too. iCatCare suggests "just a few minutes to begin with."
Never let them "fight it out." And never reach in to split up a fight. The Cornell Feline Health Center warns that you "can be seriously injured" if you do. The FelineVMA guide suggests a pillow, cushion or toy between them to break eye contact. Keep your hands clear. Cornell also says physical punishment can make a cat more afraid. It can make aggression worse, too.
Give Each Cat Its Own Everything
Cats who don't have to share have less to fight over. iCatCare says each cat needs its own bowls, bed, litter box and scratching spot. Then add "one extra" of each, spread out around the house.
The litter box math is simple. Cornell's rule is "as many boxes as you have cats, plus one." For two cats, that's three boxes, in three different places.
Height helps too. A cat tree or a cleared shelf gives a nervous cat a way out of a standoff. Cat vets call this vertical territory. It just means space up off the floor.
This is also how a diffuser gets a fair chance. If you use the kit above, run it nonstop for at least one full 30-day refill. Only then judge it. Pair it with separate bowls, beds and boxes the whole time. No plug-in can make two cats share one litter box. For the evidence, see what the research on pheromone diffusers says.
Watch Their Body Language
Some hissing is normal in the early days. Humane World for Animals puts it plainly. "A hiss here or there is not a concern," it says, if the cat also shows some good signs. So look at the whole cat, not just the sound.
✅ Going well
Relaxed bodies, and lying on one side. Normal eating, drinking and litter box use. Playing and grooming as usual. Sniffing the other cat's things, then walking off. Rubbing cheeks on furniture and doorways.
⚠️ Time to step back
Wide pupils, ears flat back, a puffed-up tail or an arched back (Cornell lists these as signs of aggression). A tail tucked under, or whiskers pressed flat (signs of fear). Growling, pacing, or peeing or pooping outside the box. Chasing, ambushing, swatting or biting.
If you see signs from the second list, go back a step. iCatCare says to "replace the barrier and go back a step." VCA's advice is to return to the last step that went well. The FelineVMA guide suggests staying there for a few more days. Then try again.
The UC Davis vet school says the same about chasing and swatting. Put the newcomer back in her room, and go more slowly. Going back is part of the plan. It isn't a sign that the plan failed.
Know When to Call Your Vet
Some trouble isn't about the new cat at all. A cat who hurts may hiss, swat or hide from everyone. Cornell says the first step with an aggressive cat is to rule out a medical reason.
⚠️ Call your vet if you see any of these
- A bite, a limp, a swelling or any wound after a scuffle
- A cat who won't eat, or who hides for days
- Sudden aggression from a cat who used to be calm
- Peeing or pooping outside the box that keeps happening
- Fights that don't settle, even after you've gone back a step
Sudden aggression or hiding in a cat who used to be calm can mean pain. Injuries from fights always go to the vet.
If your vet finds no medical cause, ask about a behavior expert. iCatCare says your vet team may know "a local, qualified clinical animal behaviourist" who can help. Cornell points to a veterinary behaviorist when simpler steps don't work.
A month from now, the carrier will be back in the closet. Your two cats may not be curled up together yet. Maybe they'll nap at opposite ends of the couch. That counts. Go at their pace, back up when you need to, and let the slow way do its work.
Questions this guide did not cover
Is it easier to add a kitten or an adult cat?
It may help to pick a kitten. VCA Animal Hospitals says it may help to choose a younger kitten to join an adult cat. It also suggests cats with compatible personalities. The slow steps stay the same either way.
How long should a new cat stay indoors?
At least two to three weeks. International Cat Care recommends that for a new cat. It notes that some cats take several weeks to feel at home.
Can I use a carrier or harness for the first meeting?
Some vets suggest it. The Cornell Feline Health Center describes cats at opposite ends of a room, in carriers or on harnesses. They can see and smell each other but can't touch. Only try it if your cat already accepts a carrier or harness calmly.
What if a cat starts peeing outside the box during this time?
Call your vet first. A FelineVMA guide on house-soiling says every cat that starts needs a thorough physical exam and a urine test. It also notes that a cat who blocks the way to a litter box can push another cat to go elsewhere.
Related reading
- Do Cat Pheromone Diffusers Work? The Evidence and a Fair Trial
- Why Does My Cat Hide From Guests? A Calm Holiday Plan
About this article
Researched and written by the LitterBond Team. Sources include the Feline Veterinary Medical Association (FelineVMA, formerly AAFP), the Cornell Feline Health Center, International Cat Care, VCA Animal Hospitals and bestfriends.org. Reviewed and updated November 3, 2026. LitterBond does not employ veterinarians; for medical decisions about your individual cat, always consult your veterinarian.
