Plan on two to four weeks, and expect the resident cat's sense of territory to be the harder problem, not the newcomer's fear. The mistake that produces most failed introductions is the same one every time: putting both cats in the same room on day one and letting them "sort it out". Cats build tolerance through smell and controlled contact, not through a fight that ends in a hiding place.
Before the Cat Comes Home
Set up a base camp: one spare room with a door that closes, containing a litter box, food and water at opposite ends, a bed, a scratching post and something to hide under. The newcomer stays in there for the first week, which is not cruel — it is the smallest space in which a cat can feel in control. Get a vet check within 72 hours: FIV and FeLV testing, deworming, flea treatment, vaccination status, and a stool check if diarrhoea is present. Do not skip the FeLV test in a multi-cat house. Pheromone diffusers are widely sold for this and the evidence is thin; buy one if you like, but do not rely on it in place of the steps below.
Days 1 to 3: Nothing But Scent
No visual contact at all. Rub a soft cloth on the newcomer's cheeks and forehead, then leave it near the resident cat's bed, and do the reverse. Swap bedding between the two spaces. Feed both cats on opposite sides of the closed door, starting with the bowls a metre apart and moving them closer by 10 to 15 cm a day, but only while both cats are eating calmly. If either stops eating, whines, or stares at the door, move the bowls back two steps. This feeding-at-the-door step is the core of the whole protocol: it teaches each cat that the other's smell predicts food.
Days 4 to 10: Swap Sides
Move the cats between rooms for 20 to 30 minutes a day so each one explores the other's territory while the other is shut away. This spreads both scents through the house and reduces the "invasion" quality of the newcomer's arrival. Then open the connecting door 2 to 3 cm, or use a baby gate with a sheet over it, and feed on either side. Widen the gap over several days. At every stage the rule is the same: calm eating means progress, and a cat that stops eating means you went too fast.
First Meetings
Five to ten minutes, in a room with an escape route and no dead ends. Scatter treats on the floor so the cats are heads-down and near each other without forced contact. Do not hold either cat, and do not carry one toward the other. Hissing, a raised paw without claws, and a low growl are normal and should be allowed to happen — they are the negotiation. End the session while it is still calm, even if that means two minutes. Repeat daily, adding a few minutes each time the session ends quietly.
What Progress Looks Like
You are looking for tolerance rather than friendship. Good signs: eating in the same room, sleeping in the same room at a distance, passing each other without a stare, sniffing noses briefly and moving on. Cats that ignore each other are a success. Grooming and sleeping in contact may come months later, or never, and a household where two cats coexist without conflict is a normal outcome.
What Not to Do
Don't put the newcomer in a carrier in the middle of the living room for a family viewing; a cat that cannot retreat learns to fear the other cat. Don't punish hissing or swatting with a tap or a shout — the punishment lands on the association between the two cats, not on the behavior. Don't feed them side by side from one bowl, and don't move the resident cat's furniture to make room. Don't bathe either cat to "reset" the scent; it removes the familiar smell and makes the newcomer more alien, not less.
When to Slow Down or Stop
Back up a stage if you see: chasing that ends with one cat cornered, fur flying, a bite that breaks skin, hissing that continues for more than a few seconds, or one cat hiding and refusing to eat or use the litter box. Separate them and go back to scent swapping for a week. Do not let them "work it out" — a real fight between cats is memorable, and one bad encounter can set the relationship back months. If a cat is injured, or if after three weeks there is no improvement, get a behaviorist involved rather than escalating exposure.
Frequently asked
How long does introducing a new cat take?
Two to four weeks is typical for tolerance, and two to six months for anything resembling friendship. The pace is set by the slower cat, not the calendar. Rushing produces hiding, spraying and fights that take longer to undo than the extra week would have cost.
Will my two cats ever get along?
Most reach a workable truce, and many become companions, but a minority settle into polite avoidance, which is a fine outcome. What matters is no conflict, free access to resources, and both cats eating, sleeping and using the litter box normally. If those hold, the relationship is good enough.
Should I get a kitten so my cat has company?
Only if you want a second cat for yourself. Cats are not universally social, and a resident adult may find a kitten stressful rather than enriching. A kitten also has different needs and energy, and the introduction still takes the full protocol. For a lonely cat, more play and vertical space is the cheaper first step.