How To Introduce New Pets To Your Existing Ones

Most people land here because a new animal is about to come through the door—or already has—and the household balance feels fragile. One rushed meeting can set patterns that are hard to unwind: fear, chasing, guarding, or a quiet, ongoing tension that never quite settles.

Calm introductions are less about a single “first hello” and more like letting two sets of senses map the same landscape, slowly. Scent first. Distance next. Short, supervised moments, then longer ones—only when both animals stay loose and untroubled.^{1, 2, 3}

Before anything else: set the house up for success

Introductions go better when the environment does some of the work. Think of the home as a series of safe pockets, with doors and barriers that let you control who goes where, and when.

Do a quick health and safety check

• Vet check and parasite control: make sure all animals are in good shape and up to date, so illness or discomfort doesn’t add friction to the first weeks.¹
• Remove flashpoints: in shared areas, put away high-value items (food bowls, favourite toys, chews) until everyone is settled.¹
• Plan for management: have leads, baby gates, closed doors, and a quiet room ready before you attempt any face-to-face time.^{1, 3}

Create separate retreats (not just separate rooms)

Each animal needs somewhere it can relax without being watched, followed, or cornered. Set up at least two “retreat zones” with bedding, water, enrichment, and a way to leave without passing the other animal.

For cats, add vertical escape routes—perches, shelves, a tall scratching post—so they can observe from above and step away without a chase.⁶

Neutral space matters—especially for dogs

For dog–dog introductions, first meetings are often easier outdoors on neutral ground, with two handlers and plenty of room to move. The goal is not nose-to-nose contact, but parallel calm: walking, sniffing the world, and noticing each other without pressure.¹

The hidden engine: scent first, faces later

Dogs and cats read one another through scent long before they are ready for close contact. When you let them gather information safely—without a looming body or a doorway standoff—you reduce the chance that “new smell” becomes “new threat”.^{1, 2, 3}

A practical scent-swapping routine

1. Swap bedding or cloths: place a lightly scented item in the other animal’s area, away from key resources (food, water, litter, favourite sleeping spots).³
2. Let them choose the distance: allow sniffing and investigation at their own pace. No holding, no forcing, no “just be friends”.³
3. House rotation (when safe): let one animal explore the other’s area while the other is comfortably secured elsewhere, so the home becomes familiar to both without direct contact.^{1, 3}

Step-by-step introductions by pet type

Dog to dog

Start outside, on neutral ground, with two adults handling one dog each. Keep leads loose, create space, and reward calm behaviour. If they can walk side-by-side without stiffening, staring, or lunging, you can gradually shorten distance over multiple short sessions.¹

Back at home, begin supervised time in open, neutral areas (yard or a room the resident dog doesn’t guard). Keep sessions short, then separate again before anyone gets tired, hungry, or over-aroused.¹

Cat to cat

Cats often need more time than we expect. The settling period can take weeks to months, and the most common driver of ongoing tension in multi-cat homes is not “personality”—it’s resource layout (too few, too close, not visually separated).²

• Use a transition room: keep the new cat in a dedicated space at first, fully set up with litter, food, water, sleeping spots, scratching, and hiding places.²
• Progress through stages: scent introduction, then scent transfer, then supervised exploration of shared spaces, then visual contact through a barrier, then closely managed sessions in the same space.²
• If any cat becomes distressed: stop and return to an earlier step for a few days. Rushing tends to create long-term fallout.²

Dog (or puppy) to cat

Begin with physical separation: closed doors and a solid barrier, ideally with a buffer space so paws and noses can’t meet under a door. Start with scent swapping, then allow each animal to explore the other’s area while the other is secured, then move to brief, calm visual sessions through a gate or screen.³

When you do introduce them in the same space, keep the dog on lead and give the cat genuine escape options (height, hiding spots, an open doorway to a safe room). Never punish either animal for stress signals—punishment tends to make the other animal’s presence feel more dangerous.³

Birds, reptiles and small pets

For small animals, “introduction” usually means safe coexistence, not direct contact. Many are prey animals, and even a playful dog or curious cat can injure them in seconds.

• Use secure housing: stable enclosures with safe latches, positioned out of reach.
• No unsupervised access: even “just for a minute” is when most accidents happen.
• Reptile care needs are specific: check enclosure, heating, UV (where relevant), diet and handling guidance before you add the stress of other pets nearby.⁴

Reading the room: what to watch for (and what to do)

During early sessions, you’re watching for comfort, not friendliness. Curiosity is fine. Ignoring is fine. Calm is the prize.

Signs you can keep going

• Loose bodies, soft movement, sniffing the ground, easy disengagement.
• Choosing to move away and then returning voluntarily.
• Eating treats or engaging with toys while the other animal is present (at a safe distance).

Signs you should pause and separate

• Stiff posture, hard staring, stalking, raised hackles, guarding doorways or resources.
• Growling, snarling, lunging, snapping, persistent chasing.
• For cats: tail lashing, hissing, growling, hiding for long periods, refusing food or litter changes after sessions.²

If things tip over, end the session without drama. Separate calmly, give everyone time to decompress, and return to an earlier step next time.^{2, 3}

Reinforcing calm behaviour (without making things worse)

Reward-based training is the safest default for introductions: it builds predictable routines and helps animals learn what earns space, safety, and good things. Harsh corrections and aversive tools can increase fear and stress, which often shows up later as aggression or avoidance.⁵

• Reward what you want: looking away, choosing to settle, responding to their name, moving with you.
• Keep sessions short: finish while both animals are still calm.
• Feed separately at first: shared food spaces create fast competition.

When to seek professional help

Some households need expert support early—especially when there’s a history of reactivity, fear, guarding, or past fights.

• Seek help urgently if there are bites, injuries, repeated attempts to attack, or a smaller animal is being hunted.
• Seek help soon if tension persists for weeks, either animal stops eating normally, or one becomes increasingly withdrawn or vigilant.²

Start with your usual vet to rule out pain or medical contributors, then ask about referral to a qualified veterinary behaviourist. In Australia and New Zealand, you can also look for veterinarians with advanced behaviour credentials through the Australian and New Zealand College of Veterinary Scientists (ANZCVS) Veterinary Behaviour chapter resources.⁷

References

1. RSPCA Australia Knowledgebase: How should I introduce my new dog to my existing dog?
2. RSPCA Australia Knowledgebase: How should I introduce a new cat or kitten to my existing cat?
3. RSPCA Australia Knowledgebase: How should I introduce my new dog or puppy to my existing cat?
4. RSPCA Australia: Caring for your reptile
5. American Veterinary Society of Animal Behavior (AVSAB): Position statements (including Humane Dog Training Position Statement)
6. RSPCA South Australia: The Dog Adoption Handbook – Making introductions
7. Australian and New Zealand College of Veterinary Scientists (ANZCVS): Veterinary Behaviour chapter (administration and resources)
8. Australian and New Zealand College of Veterinary Scientists (ANZCVS): About the College