There are many reasons to add a second cat to the house, including giving a home to another homeless cat, providing a latchkey cat with feline company, and “why stop at one, when two are more fun?”

How do you introduce New Cat to Resident Cat and vice versa?

“Tabatha, meet Tony, the resident cat. Tony, meet Tabatha, your new feline housemate. I’ll leave you two alone so you can get to know one another.”

If only it were that simple.

One of the keys to a mutually satisfying multi-cat household is making sure that your current cat and your new cat start off on the right paw. This requires some knowledge, forethought, and finesse on your part. Though each cat is unique, fortunately there are a number of cat introduction techniques that work on most cats, most of the time. Here are the main steps to ensuring a low-stress transition and lots of happy purrs.

Phase 1: Select a Cat Who’s Compatible with Your Current Cat (Unless the Cat Selects You)

Whenever possible, a high-energy kitten or young cat should be paired up with another high-energy kitten or young cat, so each has a compatible feline playmate. In general, try to match New Cat to Resident Cat. For example, if Resident Cat is older and stately, he may not appreciate a rambunctious kitten. Granted, sometimes New Cat is a stray who finds you rather than the other way around, so you just have to do the best you can.

Phase 2: Prepare for the New Arrival

The following proactive tasks will help the transition to a multi-cat household go more smoothly:

• Make sure the cats have sufficient territory.

Territory, from a feline perspective, is not just space (horizontal and vertical), but access to prime resources. Prime resources are objects or aspects of life that cats desire strongly on a day-to-day basis. They include:

• Elevated perches (command posts)
• Scratching posts
• Litter boxes
• Window views
• Comfy sleeping places
• Hideaways
• Playtime
• Human attention

Territory disputes are a common source of friction between cats. Ensuring that the cats feel confident about their access to territory goes a long way toward maintaining peace and harmony.

• Set up a private “welcome home” suite for New Cat, so the two cats can have their own space at first. This room should be inaccessible to Resident Cat and ideally should incorporate all the important territory and lifestyle elements described above. If you know that the new kitty is used to a specific litter box setup or has favorite toys, scratching posts, or sleeping surfaces, try to include those in the room; the continuity will be comforting to her.
• Make sure that New Cat gets a veterinary exam –including testing for the feline immunodeficiency virus (FIV) and feline leukemia virus (FeLV) – before coming home, and that Resident Cat has had a recent veterinary checkup and is current on the vaccine program you have set up with your veterinarian. If New Cat tests positive for a contagious disease, discuss various options, and their associated health and psychological implications for both cats, with your veterinarian.
• Spray Feliway periodically or use a Feliway diffuser in New Cat’s room and in the rest of the house. Feliway is an artificial pheromone product that often has a calming effect on cats and may ease territory-related anxiety.

Phase 3: The Debut of Cat Number Two

The “Welcome Home” Suite and Introducing the Cats to Each Others’ Scents

When the big day arrives, and you show New Cat her new lifetime home, place New Cat in her well-appointed quarantine quarters. Open her carrier and let her walk out at her own pace. Give her time to adjust to her private space. Resident Cat will know something’s up, but at least initially he won’t have to directly contend with a competitor during daily routines.

Let each cat sniff the other’s scent. Rub a cloth or sock on New Cat and take it to Resident Cat so he can investigate it with his discerning nose. Give Resident Cat a favorite treat and/or indulge him in activities he likes, such as playing or brushing, to help him make positive associations with New Cat’s scent. Then perform this sequence in the other direction – rub a cloth or sock on Resident Cat, take it to New Cat, and so forth.

After a day or two, and possibly with some human volunteers to help you, have the cats switch places for a little while. Resident Cat can thoroughly check out New Cat’s temporary room, and New Cat can have the run of the house. Both cats will take in loads of information from sniffing, and leave their scents in every spot that’s strategic from a feline point of view.

Stress-busters such as interactive playing, ample scratching opportunities, catnip (for cats who enjoy it), and luxurious petting sessions may significantly help both cats adjust to their new living situation.

Phase 4: Managing “Getting to Know You” Visits Between Resident Cat and New Cat

At some point the cats will be ready to meet face-to-face—and that will kick off the next-to-last phase of the introduction process: a series of cat-to-cat meetings that let the two cats become comfortable with being in the same place at the same time.

Use your best judgment on when to have the initial meeting. Every cat-to-cat relationship proceeds at a different pace. If both cats seem to be more or less settled and doing normal cat activities, perhaps they’re ready to see, not just smell each other. With two kittens, this could be an hour or two after New Cat’s arrival. With two curmudgeonly cats who are set in their ways, you might have to wait a couple of weeks or more.

There are several well-tested variations on how you can set up and direct this series of meet-ups. But first, here are the basic guidelines that apply to all the techniques:

• Keep the cats safe, confident, and in as good a mood as possible.
• Expect and accept growling, hissing, and some hostility, but do not let the cats engage in an actual fight.
• Use treats and other positive rewards and incentives—including ample praise.
• Gradually increase the cats’ exposure to one another, but don’t rush things. Your patience will pay off.
• Chaperone the initial meetings. Keep this up until you’re reasonably sure that neither cat will hurt or torment the other. As the two cats become more comfortable with one another, give them increasing freedom to interact with each other.
• At the end of each meeting, return New Cat to her temporary private quarters.
• Exude an upbeat calmness, which hopefully will be picked up by the cats.
• If you need to break up a fight, say “no” very loudly, clap your hands, stomp your feet, throw a towel between the two cats, or squirt them with water. If, as a last resort, you have to position yourself between the cats to end a fight, wear shoes, socks, and long pants, and have a pair of thick oven mitts nearby, to protect your hands from bites and claws.

Here are some of the most favored techniques for allowing the cats to get acquainted:

• With the aid of a doorstop, open New Cat’s door a crack. Let the cats check each other out. Feed each cat their favorite meals, their bowls on opposite sides of the door.
• Use a baby gate—or two baby gates, one on top of the other—to separate the cats and proceed as in the previous technique.
• If the cats are amenable to being on a leash, and you have a human assistant, let the cats meet each other while on leashes. The leashes should be short and the humans should keep a tight grip on them.
• Feed the cats in opposite corners of a large room. It helps considerably to have an assistant when implementing this option.
• Initiate dual play sessions, so that each cat gets to chase, swat at, and pounce on his or her own target. This technique is also much easier to do with two people. Give the cats plenty of praise, and offer them treat rewards when playtime is done.

Let each meeting continue as long as the cats are being civil to one another. Tolerate growling and posturing, but if they start to fight, or if one of the cats is clearly traumatized, end the visit. It‘s better to have fifty brief visits that go well than to have one extended visit that ends in injuries and a trip to the vet.

There’s no upper limit on the amount of brief meetings to have before the cats are free to roam the house unsupervised. With two kittens, the whole process could be over in less than a day. Two stubborn adult alpha cats may need several weeks of limited face time before they’re ready to be left alone in the same room.

Phase 5: Settling Into One Big Happy Family

When the cats are generally going about their business in the presence of each other and seem to have reconciled that they have a permanent feline housemate, you can ease up on the supervision. Let New Cat have access to the entire house—at least the part where cats are allowed. Keep an eye on things.

Double-check that the cats have sufficient territory. Rearrange the layout if necessary, to help foster peace and minimize inter-cat bickering.

The Welcome Home room should stay in place for a while, until New Cat doesn’t use it as a refuge.

Considering that cats in the wild are primarily loners, it’s amazing how well most of them adapt to living with feline company under the same roof. In many cases, the cats become best buddies—playing, sneaking around, and snoozing together. While tempers may flare during the introduction period, once that settles down, usually everyone can relax and enjoy the start of new, beautiful friendships.