Haven't had time to post pictures online yet of my fur babies, but now that we finally have the new cat Moon Beam inside, I am heartbroken to realize my cats aren't as animal friendly as I had thought. We have 2 dogs and 2 cats before brining Moon Beam in. Both dogs get along well with her, and she doesn't seem scared or violent toward them at all. But our two cats who get along with each other with the exception of small fights once in a blue moon - do not accept the new cat at all. We've kept them on different levels of the house and slowly try to bring them together but every time they are in the same room Henry and Kovu growl and go after her. Moon Beam used to just stand there and take it, or run, but she has started to fight back with them as well. Is there ANYTHING I can try to smooth the transition? If not out of fairness to all three of them we will be trying to find her a new home. If we can not find someone to take her, or a foster, we will be taking her to the shelter (not by my choice). I can't stand the thought of her going somewhere she won't be well taken care of, and I'm scared she'll end up outside in the cold again. :(

Have you tried introducing her to one of the boys at a time? Swapping out things with her scent on it between the cats.

Feli-way is a pheromone product that comes in different forms to help easy the cats' anxiety. You could get collars for each of them or a diffuser in a main room with her and then try bringing one in at a time.

I have a ton of cats and they usually growl at each other for the first couple days and then theyre fine...i just recently had a momma and 3 kittens dumped at my house and she use to hiss and bat at my orange cat and now she lets him eat with them...usually it only takes a few days...

I have 6 cats at one house 

3 cats at another plus the momma cat and her 3 babies plus around 7 wild cats

I too have tiny cat fights but theyre never serious!

No suggestions since I'm not really a "cat person", but good luck! I'm sure you can get it figured out :)

Paints since 6-8-14

Cats can take weeks or even months to get used to each other, depending each one's temperment. (I still have some cats that really don't like each other - they just stay in separate areas and try not to cross paths, lol.) I second what trig says about putting things that smell like her with them. 

We've still just been keeping them seperated... I'm going to try to get a hold of our cat carrier (I'm not sure where I last had it or if I loaned it out) and put Moon Beam in it and try to coax Henry and Kovu to get used to her that way... We've had Henry the longest. He's a large long haired cat and is around 7/8 years old. Kovu is a female actually lol (we thought she was a boy first and the name stuck) and she is 3-5 years old and very small for her age. (I can't remember what year my sister found her) - and we haven't taken Moon Beam to a vet yet because we aren't sure if we are keeping her but I am assuming she is younger than Kovu or wasn't well taken care of before they let her go (shocker). She was very skinny and small when we let her inside we soon found she wasn't litter trained (even though they said she was lol) - so we are also battling that. I've never had such a hard time with a cat, but she's been through so many changes in her life that I'm sure she's just stressed out and doesn't feel like anywhere is home. I'm just scared to leave them alone because if the dogs knock out the gate that seperates them from the downstairs/upstairs I don't want them to hurt each other. Henry and Kovu are declawed in the front, Moon Beam is not yet as I was thinking of getting the claw caps thing time instead. I just wish they liked each other better. I will have to look up Feli-way!!

Honestly i wouldnt confine the new cat in a carrier with the other two...it might make mer more fearful, cuz she may think she cant get away from danger...

Older cats just take longer to adjust to new kitties...

Ive brought so many different cats in and out of my houses and it literally only takes a few days for them to get use to each other...

I introduce and my older cats hiss and growl and either run away or bat once and then walk away...

So i usually start playing with them with their string toys and most cats cant resist to play!!!