I take care of about 30 feral cats outside and I occasionally have to take them in from time to time so I have experience in getting cats to get along with new kittens. Here are some tips on how to introduce a new cat or kitten to your existing cat at home. Expect the transition to take at least 2 weeks for them to get used to each other. That means do not leave the newly introduced cat alone in your home with the older cat. They should be separated while you are not home by putting the new cat in a closed bedroom or a bathroom. Never confine the older cat, after all it was the existing cat’s home first.
No matter what kind of behavior is being displayed by your first cat never discipline her or ignore her in favor of the new cat. It is very important to pay as much attention to your first cat as you do the kitten so that your older cat does not feel neglected because of the new arrival. The negative behavior that will be displayed by the older cat is normal. It is her way of establishing a pecking order or dominance. My eldest cat is the alpha female of our brood and she lets the younger cats know about it by hissing, swatting at them and by always glaring at the others with her ears back. Some cats are more submissive and will shy away from the new cat, it all depends on your cat’s personality.
I would suggest bathing the new cat to get rid of any foreign smells. Sometimes a kitten will be too young for a bath but you will want to have the cats smell as much like each other as possible so you can put a little baby powder on them or wipe them down with a scented baby wipe.
You can keep the cats apart in the beginning and then gradually introduce them. You absolutely must supervise the cats when they are together for about an hour a day gradually increasing the time until the older one tolerates the younger cat. In my experience this takes at least 2 weeks before you will be able to leave them alone in the house while you are not home. Until they are acclimated to each other they should stay in different rooms while you are not present to referee.
Here are some tips to make the merging process easier,
If you have a choice of gender when choosing your new cat pick the opposite gender. For instance if your cat at home is a female choose a male kitten.
Make sure the older cat is neutered. Cats that are fixed are generally more calm.
Bathe both cats with the same shampoo, Johnson & Johnson lavender baby shampoo works great. You can bathe a kitten with it since it is not a flea shampoo just make sure you keep the kitten warm until it is dry.
Use a cat carrier to keep the kitten in for the first few days.
Do not interfere when the cats are hissing at each other. If the fight gets to nasty spray them with a water bottle.
Feed the cats separately and feed them something they would really enjoy like canned cat food instead of dry.
Spoil your older cat with attention instead of the kitten.
Catnip does wonders, use it. There is also a product you could try called Feliway which is a behavior modifier.
If the merging of the 2 cats does not work out after you have tried for a few weeks then please find the kitten a new home. If the disposition of your older cat has changed for the worse, don’t worry, the cat will go back to normal once the new cat is removed from the house.
Click here to view the original Factoidz article including pictures How To Introduce A Cat