You can’t force your pets to like each other. We don’t have a crystal ball to predict whether or not your pets will be friends, but we do have techniques that will increase your chances of success. Most importantly, try to choose a cat with a similar personality and activity level to your current pet. An older cat or dog might not appreciate the antics of a kitten. Go slow during the introduction process to increase your chances for success. Don’t throw your pets together in a sink-or-swim situation and just hope they’ll work it out. That’s a recipe for the fur to fly!

Cats are territorial, and in general they don’t like to share. A cat who’s unhappy about a newcomer may express their displeasure by fighting with the other pet and marking territory (peeing on the floor, wall or objects). Cats also dislike change, and a new cat in the house is a huge change. These two character traits mean you could have a tough (but not impassable) road ahead.

Some cats are more social than others. An 8-year-old cat who has never been around other animals might never learn to share their territory (and their people) with other pets. But an 8-week-old kitten separated from their mom and littermates for the first time might be glad to have a cat or dog companion. All of this means that your current pet and your new cat need to be introduced very slowly so they can get used to each other before a face-to-face meeting. Slow introductions help prevent fearful or aggressive behavior from developing. Below are some guidelines to help make the introductions go smoothly. The introduction process can take anywhere from a few days to a few weeks, or even a few months in extreme cases. Be patient.

Confinement

To allow time for the newcomer to adjust to you and their new situation, keep them in a small room with their litter box, food, water, scratching post, toys and a bed for several days to a week. Feed your resident pets and the newcomer on each side of the door to this room, so that they associate something enjoyable (eating!) with each other’s smells. Don’t put the food so close to the door that the animals are too upset by each other’s presence to eat. Gradually move the dishes closer to the door until your pets can eat calmly while standing directly on either side of the door. Try to get your pets to interact with a toy. Tie a toy to each end of a string, then place it so there’s a toy on either side of the door. Hopefully, they’ll start batting the toys around and maybe even batting paws. Be sure to spend plenty of time with your new kitty in their room, but don’t ignore your resident cat.

The Old Switcheroo

To animals, smells are far more important than appearances, so you want to get your pets used to each other’s scent before they meet face-to-face. Swap the blankets or beds the cats use, or gently rub a washcloth on one cat’s cheeks and put it underneath the food dish of another. If there are more than two animals in the house, do the same for each animal. When the pets finally do meet, at least their scents will be familiar. Once your new cat is using their litter box and eating regularly while confined, let them have free time in the house while confining your other pets to the new cat’s room. It’s best to introduce your new cat to a room or two at a time and increase their access to other rooms over a few days. This switch provides another way for them to experience each other’s scents without a face-to-face meeting. It also allows the newcomer to get familiar with their new surroundings without the other animals frightening them. You can do this several times a day, but only when you’re home to supervise. If you have to leave the house, put your new kitty back in their room. Next, after you’ve returned the cats to their designated parts of the house, use two doorstops (one on each side of the door) to prop open the dividing door just enough to allow the animals to see each other. Repeat the whole process over a period of days—supervised, of course.

Slow and Steady Wins the Race

It’s better to introduce your pets to each other gradually so that neither animal becomes afraid or aggressive. Once the cats are face to face, though, there will be some kinks for them to work out. If you’re really lucky, your cats may do some mutual sniffing and grooming, and you’re on your way to success. They may sit and stare at each other. You can provide distraction by dangling toys in front of them at the same time. This may encourage them to play together. They might sniff each other, hiss and walk away. That’s to be expected. This may go on for a few days or so, and then you’ll probably find them both sleeping on your bed.

Breaking It Up

If you’re not so lucky, they may be very stressed. They may only posture and make a lot of noise. But, as soon as there are signs of increasing aggression (flattened ears, growling, spitting and crouching) make a loud noise by clapping your hands or throw a pillow nearby to distract them. If the standoff continues, very carefully herd them into separate parts of the house to calm down. This could take up to 24 hours, and the cats may take out their stress on you.

Be Careful

If the cats fight repeatedly, you may need to start the introduction process all over again and consider getting advice from a vet or animal behaviorist. Note: Never try to break up a cat fight by picking one up. You’re bound to get hurt.

Reducing Tension

There are other things you can do to help ease tension between feline roommates. Have your cats examined by your vet before introductions to make sure they’re all healthy. Have one litter box per cat plus an extra one. Try to keep your resident pets’ routine as close to what it was before the newcomer’s arrival. Make sure all cats have a “safe” place to escape to.