The instinct when bringing a new pet home is often to just let everyone meet and see how it goes. RSPCA guidance takes a more deliberate approach for good reason — a bad first impression between animals can create tension that takes months to undo, while a properly managed, gradual introduction gives a much better chance of a genuinely settled household.
The general principle: slower than feels necessary
Across species combinations, the consistent theme in RSPCA and veterinary behaviour guidance is that gradual, controlled introductions produce better long-term outcomes than a fast, direct meeting. Evidence and professional experience both suggest this process often takes at least a week, and sometimes considerably longer, particularly for cat-to-cat introductions or cats and dogs. Trying to rush a resolution because you’re keen for everyone to get along tends to backfire.
Before the new pet arrives home
- Set up a separate base room for the newcomer — with its own food, water, bed, litter tray (for cats) and hiding places — so it has secure territory from day one rather than being thrown into shared space immediately.
- Keep resident pets and the newcomer fully separated at first, with no direct contact, while everyone settles and adjusts to new smells and sounds in the home.
Scent swapping, before any visual contact
RSPCA guidance recommends swapping scent between animals before any face-to-face meeting — exchanging bedding, or gently stroking one animal then the other without washing your hands in between, so each becomes familiar with the other’s scent in a low-pressure way. This step is easy to skip because it doesn’t look like “real” progress, but it does meaningful work in reducing the shock of a first physical meeting.
Introducing cat to cat
- Keep the new cat in its own base room, with a full setup (litter tray, food, water, bed, hiding place, a window if possible), for several days to a week before any direct contact.
- Swap scent via bedding, and allow each cat to explore the other’s space (while the other is elsewhere) so scent becomes familiar before any face-to-face meeting.
- When you do introduce them visually, keep sessions short, calm and supervised, ideally with a barrier (a cracked door, a stairgate) at first, and let both cats retreat if they want to rather than forcing proximity.
- Watch for hissing, growling or swatting as signs to slow down and extend the separated phase rather than push through it.
Introducing a new dog and a resident cat (or vice versa)
- Keep the new arrival in a separate, fully equipped space at first, allowing the dog to become familiar with the cat’s scent from under a door before any visual introduction.
- When introducing visually, keep the dog on a lead and under close control, and ensure the cat always has a clear, easy escape route — never corner or trap either animal during an introduction.
- Feeding both animals on either side of a closed door (or, later, a see-through barrier) can help build a positive association between the new animal’s presence and something good happening.
- Keep initial sessions brief and end them calmly, before either animal becomes overstimulated or stressed, rather than waiting for signs of distress to appear.
Signs it’s going well, and signs to pause
Going well: curiosity without fear, relaxed body language, animals choosing to be in the same space voluntarily, normal eating and behaviour continuing throughout. Signs to pause and go back a step: persistent hissing, growling, swatting or lunging, a resident pet hiding more than usual or going off food, or any physical altercation, however minor. If you pause, that’s not a failure of the process — it’s the process working as intended, and it’s normal to need to repeat an earlier stage.
When to get extra help
If introductions aren’t progressing after a few weeks of consistent, patient effort, or if there’s been any aggressive incident, it’s worth getting input from your vet or a qualified animal behaviourist rather than continuing to manage it alone — ongoing tension between household pets is a genuine welfare issue for everyone involved, not just an inconvenience.