Help! Resident Cats Attacking New Cat After Months of Slow Introduction
I have three cats and I’m struggling with introductions and behavior. I adopted two sister cats (littermates), Minnie and Maple, from the shelter in December 2024. They're 20 months and it was just the two of them for about a year. Then in December 2025, I adopted a third cat, Willow, She is 7 months
When I first brought Willow home, I kept her in my bathroom for about three days so she could decompress. After that, I moved her into my bedroom, where she stayed (along with access to the bathroom) for about two months, completely separated from the other cats. During that time, I did scent swapping, and Minnie would come up to the bathroom door and interact with Willow by playing under the door. Maple, on the other hand, would mostly just watch from a distance and didn’t really engage.
About a month after getting Willow, I tried introducing them. Maple immediately didn’t like her, she was growling and hissing so I went back to keeping Willow separated in my room. Then around February 2026 (about 2 to 2.5 months after bringing Willow home), I let Willow out into the rest of the house. At first, Minnie and Willow seemed to get along fine. They were sniffing each other, playing, and there was no aggression. Maple still didn’t like Willow at all.
Over the past month, things have gotten worse. Maple started attacking Willow whenever she sees her, and now Minnie has also started joining in and attacking her too. I’ve tried separating them and rotating spaces, keeping Willow in a bedroom while Minnie and Maple are in the cat room, and switching them out. I also tried keeping Minnie and Willow together, but after a few nights I noticed Minnie was also being aggressive toward Willow. Now I mostly keep Willow separated because she seems scared.
At this point, Willow is getting attacked by both cats, and I don’t want her to live like that. I adopted her from a shelter that said I could return her at any time, but I really don’t want to. I want to make this work. I just don’t know what else to try, so I’m looking for any advice, suggestions, or similar experiences.