I'm sorry about your grandma. How old is her kitty?

Your plan sounds good. The only thing I have to add is maybe getting a couple of those "Feliway" gadgets that plug into electric sockets. They dispense the "friendly" hormones of cats and help to keep things calm.

Good luck...

The under-door and scent-swapping strategy is too incomplete for my liking. I prefer and have had excellent success using baby gates to fill the doorway between the newbie's room and the rest of the house. Baby gates allow the newbie to become acquainted with the sights and sounds of the household and its residents from the safety of his side of the gates. The gates allow full visual and auditory contact but restrict physical contact. The newbie and resident animals can approach each other, talk to each other, hiss and growl at each other, charge each other, and/or extend friendly greetings toward each other - all without significant physical contact. It's a great way to let them get whatever they feel they need to get out of their systems before they actually have physical contact.

Once the baby gates have worked their magic, which may take hours or months depending on the feline personalities involved, I implement Stage Two of the integration process. If the resident cats are passive toward the newbie, I put the newbie into a cat harness (NOT a collar) and long, light leash (a long piece of kitchen twine will do), and take the newbie into the rest of the house for a visit. With the harness and leash attached, I can control interactions between animals and put an immediate stop to any aggressive acts.

If one of the resident animals is inclined to behave aggressively toward the newbie, then the aggressor gets a harness and leash, as well, and is controlled by another household human.

In my experience, it is important to have this sort of physical control over these first integrative excursions. Sometimes all it takes is a single aggressive encounter to permanently set the relationship between cats. I learned that lesson the hard way. I don't believe in the "let them work it out" theory when it comes to cats. Domestic house cats are not pack animals, and they don't possess the innate skills to work out social "pack" structures like dogs do. Almost all felines are innately solitary and instinctively defend territory. They need a little guidance to learn how to live in a more social feline society.

Laurie

Once you start allowing all of the cats free access, at least initially make sure that there are plenty of food and water dishes in different locations. When I was a horse-mad teenager, I worked at a barn where the horses were turned out at night. My boss told me to always distribute the hay so that there was one more pile than there were horses... that way, low-man-on-the-totem-pole would always have something to eat even if the other more dominant horses chased him away from where they were eating.

Thanks all. These are some great tips, I'm hoping to try all of them! The new kitty was a stray, as is one of our current kitties, so we're not sure of their ages.

I kept my new kitten in the bedroom (still do when they are alone) and let my older cat have the kitchen/living room. I swap them and let them get used to the smell of each other on things. At first I would hold the kitten and let the cats see each other across the room for a minute, increasing time and decreasing distance. Then I'd sit in the living room but not let the kitten down. Sometimes I'd sit beside my older cat and pet her while holding the kitten. Now I will have them share a space but I limit the time because the kitten is a maniac who dive-bombs the cat whenever she sees her. Muffin just isn't into that, she's ok if the kitten comes out and is sitting on the opposite side of the window sill. But most times the kitten runs full tilt and jumps Muffin, wrapping her arms around her trying to wrestle. Muffin doesn't like physical interactions with other cats so she hisses and growls and swats and eventually hides under the bed.

All suggestions are good but the most important thing is to watch for any subtle sign that they are about to have a negative interaction. Once I heard a slightly different hissing/growling (little more deep and intense) and I saw that both tails were poofed out and backs were arched. I separated them but that was the only time. Pay close attention and give lots of attention to your other cats so they know you still love them too.

I am sorry for the loss of your grandmother. I hope all goes well with the introduction of her cat into your household.

I know it's a difficult transition for all the kitties. I don't mean to hijack this thread but I'm going through this right now and I'm hoping to hear from people who say that it does get better.

We adopted a little kitten 10 days ago. We found her on the underpass leading to a major highway:( It's a miracle that she wasn't hurt. After a short stay at the vet, we've adopted her. We already have two cats, 22 months old, a bonded sister and brother. I never planned on introducing a new cat but there was no question that we would take her.

We sequestered her in our guest bedroom with her own food, water, litterbox, toys and basket. Prior to her arrival, we let our cats sniff her scent on a towel and a cat comb with her fur. We introduced them all after a day apart. Our girl cat hissed but our boy tuxedo was just curious and followed her around. He's since taken a few steps back...he's off his food and won't play his favourite cat dancer.

The two older cats sleep with us and we separate our kitten in her safe space over night. But the two siblings are not warming up to her yet:(

Good luck,

Here is a photo of our new kitten Lucky with Oreo:)

She is one lucky kitten alright! And so adorable!