Friendly, single adult cats can have trouble adjusting to living with a new kitten. Often, the older cats will appear sad, reclusive, hiss a lot, and sometimes even stop eating or start urinating in strange places if it isn't adjusting well to the new member of the family.

These behaviors occur because cats do not like change, especially when it involves their established territory. Introducing a kitten to an adult cat can cause a lot of stress in your household, but there are some things you can do to help make the introduction go more smoothly.

Preparation is the key to a successful introduction of a new kitten to your older cat. If you prepare your cat for the new arrival and make the changes seem less drastic, then it is more likely to adapt to its new roommate. Setting out new bowls and items for the kitten in advance is an important step, and being sure to establish boundaries for both cats will help everyone adjust. Overall, be sure to give yourself (and your older cat) plenty of time to prepare for this adjustment with these steps.

Preparation

Calm Your Older Cat

Pheromones are useful for creating a calm environment for any cat. The weeks before the arrival of a new kitten is a great time to make use of them. Diffusers, sprays, and wipes are all available and help your cat feel relaxed without the use of drugs. Try using pheromones for at least a few weeks before bringing home a kitten.

If you suspect your older cat will become stressed and anxious with a new kitten, consider nutritional supplements that are designed to calm a cat. These won’t drug your pet but will help it remain calm and relaxed. They typically work best if given a few weeks prior to the anticipated stressful event and can be continued after the new kitten arrives. The ingredients usually include L-theanine, Phellodendron, magnolia, whey or milk proteins, and other natural ingredients shown to be safe and effective for pets.

Your veterinarian is a great resource when it comes to recommending safe and effective calming supplements. There are a ton of "calming products" out there today. Check with them before starting your pet on any supplement to make sure it is worth the time and money!

Get Your Home Ready

New items for your kitten, such as food bowls, beds, another litter box, and toys, should be placed in and around your home before the kitten comes home. Start putting these items in their new places about a week before the new arrival so your adult cat can smell them and get used to all the new things. If you can, try to include items that have the scent of the kitten on them already. Make sure you are ready for the kitten. If you are stressed out and unprepared, your older cat will be able to tell and be negatively affected by it.

Designate a small room, such as a bathroom, for your new kitten to retreat to and spend the first week or so in. Your older cat should be able to get to the door of this room in order to hear and smell them, but not have any interaction with the kitten. Place the kitten’s belongings in this room (such as a litter box and food bowls) along with a toy that belongs to your older cat.

Cats are typically stressed by limited access to resources. Resources include food, water, litter boxes, prime perching spots, and you. There should be a litter box for each cat PLUS an additional litter box, and these boxes should be distributed throughout the house. Cats typically do not want to cross paths with another cat when attempting to access a resource, so keep this in mind when placing resources throughout the house. Remember it is a good idea to start using pheromones and calming supplements before making any changes in your house, as this process alone has been known to cause stress-related illnesses in cats.

Prepare Your Older Cat

Make sure your older cat is healthy. Added stress to an unhealthy cat will only make things worse, and you want your cat not only mentally prepared for a new kitten but also physically ready to handle it. Take your cat in for a checkup with your vet to make sure it is healthy and that its vaccinations are current. Respiratory diseases are common in kittens, so you’ll want your older cat’s immune system to be ready to tackle anything that comes into the house. In case scratching or biting occurs between the cat and kitten, you’ll also want your cat's rabies vaccine up to date.

It is also important to know your cat and the kitten's Feline Leukemia (FeLV) and Feline immunodeficiency virus (FIV) status prior to introduction. Your veterinarian can help guide you through the recommended testing that should occur before the introduction of any new cat into a home.

While older cats will occasionally take to a new kitten right away, they typically need a little time to adjust to the changes. Sometimes cats never fully accept a new kitten but will simply coexist, keeping to themselves away from the other cat in the house. You’ll want to make sure that no matter how your cat feels about the new kitten, things stay peaceful and you have the best chance at creating a budding friendship from the start.

The Introduction

When you bring your kitten home, allow your cat to sniff it while the kitten is in a carrier. Go directly to the room you previously designated for the kitten, and allow them to explore. The litter box, food bowls, bed, and some toys should all be easily accessible. Do not let your older cat have immediate access to the kitten.

At night, when you are not home, and whenever you are unable to supervise the kitten and your older cat, keep the kitten in its designated room with the door closed. As your cat gets curious, it may stick its paw under the door, sniff under the door, and listen to the kitten. Do this for about a week. Don’t forget to pay a lot of attention to your older cat after playing with your kitten. It’ll need your attention and support, and the scent of the kitten on your clothing will help it get used to the newcomer. Just make sure to wash your hands between play sessions to avoid the spread of infections.

Encourage Time Together

After about a week, let your kitten explore the house under your watchful eye. Allow your older cat to observe this exploration and retreat if it wants to. Do not force interaction between your cat and kitten. If your cat has a favorite interactive toy, such as a feather wand or laser pointer, try playing with both cats at the same time. This will encourage mutual activity. You can also give them both treats at the same time and feed them at the same time from separate bowls. Be sure to leave enough space between the food bowls so your older cat does not feel threatened.

Encourage any positive interactions your older cat has with the kitten using praise, treats, and physical affection. You want your cat to associate the kitten with happy, positive things.

Allow Your Older Cat to Establish Boundaries

Cats need to have order, and a new member in the home must learn the rules. Your older cat may have a period of time when it tries to establish boundaries with the new kitten and may hiss and swat at the kitten when the newcomer does something unfavorable. This is completely normal and as long as it is just hissing and swatting, do your best to not interfere. Your older cat is teaching the kitten where its boundaries as the new cat are.

Problems and Proofing Behavior

They may never turn out to be best friends, but most cats learn to accept and occasionally appreciate the presence of another feline roommate. Don't give up if the first encounters are not positive. Older cats can take time to acclimate to a younger cat. A common mistake is to rush the socialization between cats and then getting mad or frustrated when it doesn't work out. Keep calm and work in increments to bring the cats together. Try timing your interactions and slowly increasing the amount of time together. If your older cat is especially aggressive toward the new kitten, speak with your vet or a behavior specialist for tips.