How to Keep New Cat From Attacking Older One

Max the Cat
Instagram @max_maxthecat

Question: "My new cat is a bully. Teach me how to introduce cats!"

Gloria shares her home with seven-year-old Sissy, and acquired eighteen-month-old spayed Bella four months ago. She writes, “Sissy is afraid of everyone and everything. She was abandoned as an eight-week-old kitten and quite feral and has been socialized to myself and an elderly cat who passed away last summer.”

During several visits to the shelter, Bella showed no sign of aggression toward other cats, so Gloria brought Bella home.

“The end of week two, Bella snuck past my foot and went into Sissy's room to meet her more closely. Sissy attempted to run and Bella gave chase. It resulted in a lot of hissing, fur flying and a bite on Sissy's neck. I didn't discover the bite until it got infected and broke open after she clawed most of the fur away,” says Gloria.

Gloria has tried several things to help the two cats become used to each other. She put them in separate pet carriers to sit beside each other, and then moved carriers to a 90-degree angle so they could see each other. With a neighbor’s help, she wrapped the cats in separate towels and allowed them to sniff each other's behinds. She also had a friend hold Bella while she contained Sissy so they could look across the closed bedroom at each other—and made sure to block eye contact if it became intense.

“I let them know they can be in the same room without being hurt.

I rewarded positive behavior with soft words and kitty treats, and sprayed with water for negative behavior (attempted charging),” writes Gloria. “I have put a harness and leash on Bella and allowed her to go into the room where Sissy is (Sissy immediately goes under the bed).  I have kept them about six feet apart.

Sissy has never shown any aggression. Bella talks to her and rapidly swats her tail and her tail puffs up. They are never left alone in the same room together. I alternate who has time with me and they are loving with me but not with each other. I don't know how to break through and move forward. Any help you can offer would be greatly appreciated.” Gloria in Oregon (madly in love with cats and wishing she had remained a one-cat family)

Amy's Answer

Gloria, don't give up! I can tell from your detailed question that you're a dedicated cat mom, and there is hope. Let's use the HISS Test to evaluate the problem; it stands for health, instinct, stress, and symptom solvers. 


I always encourage owners to have cats checked out by the veterinarian to eliminate problems. While Bella may be perfectly healthy, Sissy's age could be a factor in hidden health issues that encourage the other cat to target her.


Since Sissy has a history of being feral (or nearly so) it's not unexpected that she'd be fearful of other cats. It's that stranger danger scenario, where something automatically is deemed scary if unknown. Meanwhile, Bella isn't much out of kittenhood, and likely considers chasing Sissy a great game.

When Sissy runs, it triggers Bella's instinctive urge to pursue.


The stress of losing a cat friend, plus a recent move, AND the addition of a new cat pile on the stress in Sissy's case. Cats also react to owner stress, and I suspect that Gloria also feels quite a bit of angst over the situation.

S=Symptom Solvers

Gloria has done a lot right, and I applaud her effort to introduce the cats. I understand the reason she’s used some of the techniques, but from the description, they may not have been implemented exactly as recommended. I usually recommend some very basic cat-to-cat introduction steps, and then adjust for individual cases as needed. You may need to start over with the intros.

Probably the biggest issue we humans have when introducing cats is to rush the process. Four months is not a long time.

Cats may take six months to two years to adjust to a new kitty friend.

Cats don’t do well when forced into situations in which they have no control. Placing them in carriers can be a useful technique. But rather than situating carriers side-by-side immediately, behaviorists recommend the crates be set across the room or down a long hallway from each other, and then gradually (over several days) be brought closer together and only as long as they stay calm. If the cats are placed so close that they become upset, and have no way to escape, they essentially get to “practice” being upset in each other’s presence.

Similarly, wrapping the cats up and forcing them to sniff each other has no benefit. The cats have to WANT to allow this to happen. Think of a situation that makes you uncomfortable (maybe a hairy spider?). Would being wrapped up so you can't get away as the spider crawls over you make it any less distasteful?

The technique of holding/containing the cats in the same room while feeding treats and interrupting hard stares, containing with a leash, and keeping them six-feet or more apart are all very good techniques. Continue to stop the chase, and reward for good (calm) behavior with attention and treats. You’re doing the right thing by only allowing supervised interaction, and it’s great that they each have private loving time with you. You can also help your shy cat and boost Sissy’s confidence level by giving her lots of hiding spots and second-story (cat tree) locations to lounge out of reach.

Most of all, remember that all cats are different and introductions go only as fast as the kitties involved wish. That’s out of your hands, and in the cat’s paws so give yourself a break and let them handle this. There’s no rule that says all cats MUST be friends, and you are NOT a failure if it turns out they must continue to live separate lives to stay happy. It took my cat Seren two years to learn to tolerate the dog. She still doesn’t like him, but has decided he won’t disappear and so at least puts up with his presence.