Introducing Your Kitten to Other Cats
If you have another cat, you must isolate the kitten from it for a minimum of three days or longer if necessary to allow the kitten to be comfortable in its first room, finding its way around and gaining confidence without another cat being over-aggressive over territory. Unfamiliar cats are frightening to each other even if they are non-aggressive, so you should expect your existing cat to be frightened of the kitten to start with.
Everything should be done very gradually. It will be much better for your existing cat if it doesn’t have to meet the new kitten until the new kitten smells of your house and you. Most experts recommend making the cats smell the same as each other, either by putting scent on your hands and rubbing both the old and new ones, or by swapping bedding and toys back and forth between them. Getting the smell of you and your house into the kitten can take 2-3 days which may seem a long time, but will give your new kitten time to feel confident in its surroundings before dealing with its new housemate(s).
When it’s time to start introductions, leave the kitten in its carrying basket and let the other cat(s) come in to sniff around it in the kitten’s room – so they can all get a good look at each other without too much stress. If you have one available, a large cage can be used which would also allow the kitten’s food and litter to be on hand at the same time. In either case, repeat this exercise a few times each day over a couple of days.
Supervise the first few meetings very closely and resist the temptation to involve more humans than necessary. When you feel the cats are ready to be brought together, make sure that they all have a clear route to their places of safety without you being in the way. You might start with the door to the kitten’s room held open just enough to allow the cats to sniff at each other through the gap but not get too close. Some recommend feeding them both at the same time on either side of the door. Never force them into the same room if they are not ready yet. When you do let them into the room together there may be hissing and growling which is quite normal, but if they are very unhappy with each other put the kitten back in its room and try again later. Begin with a couple of short meetings each day then gradually give them more time together more often. Reward positive encounters with treats during and after each introductory meeting.
How you introduce your cats can have a long-term impact so it is essential to do this gradually to increase the likelihood of them forming a bond (or at least being tolerant of each other). It might take days, weeks, or months but most cats will get on with each other if they don’t feel threatened and have plenty of independent access to food, water, litter trays and friendly humans.
Some cats are quicker to integrate, particularly if the other cat is also a new kitten, so go with your gut feeling and be there to sort out any problems. Your sense of calm is important as your cats will read your mood and be reassured by it. Never leave your new kitten alone with another animal until you are confident that they will not end up fighting.
https://icatcare.org/advice/how-introduce-kitten-cat is an excellent guide that will give you plenty of ideas, and there are many other advice pages available online that will give you food for thought. We also have some on our own website from previous owners who have shared how their introductions were carried out.