A dog who has been the only pet for years has a settled map of the house: every room is his, every smell is familiar, and every routine runs through him. A cat redraws that map overnight. Settling them together works when the dog meets the cat in layers, each layer boring before the next begins, and when the cat can always get away. Think in weeks, not days, and treat quiet, uneventful sessions as the success you are aiming for.
Before the cat arrives, decide which rooms will be the cat's sanctuary at the start, ideally somewhere the dog can be kept out of without disrupting his own sleeping and feeding spots. Losing his favourite room and gaining a cat on the same day is a double blow, so rearrange as little of the dog's world as you can.
Scent Swapping Before Sight
For the first stretch, the animals learn each other by smell alone. Rub a soft cloth gently along the cat's cheeks and flanks, then let the dog sniff that cloth at home and reward calm investigation. Do the same in reverse with a cloth rubbed on the dog's chest, placing it near where the cat rests and eats.
Feed both animals on opposite sides of the closed sanctuary door, starting far enough back that each eats normally, then gradually closer across days. Eating near the other's scent links that scent with something good, and a dog who will not eat near the door is telling you the distance is still too small. Swap bedding too, once the cloth stage feels easy, so each sleeps with the other's smell woven into a place of rest.
Sight Through a Barrier Before Contact
Only when scent work looks relaxed do you add sight, through a sturdy baby gate, a mesh door, or a door opened a crack and secured. Keep the dog on a lead, reward him for glancing at the cat and then looking back at you, and end each session while both animals are still loose and disinterested. Sessions of a few minutes, repeated often, teach more than one long stare-down.
Watch for the signals that say slow down: a dog who fixes hard, whines with a stiff body, or lunges at the barrier is not ready for more access, whatever the calendar says. Equally, a cat who stops eating, hides all day, or avoids the litter tray is carrying too much pressure, so increase distance and return to scent-only days without treating it as failure.
First Shared Rooms, With the Cat in Control
Give the cat escape routes and high places before any shared time: a cat tree, cleared shelves, and a gate with a cat-sized gap or a door propped so the cat slips through and the dog cannot follow. In first meetings the dog stays on a lead held loosely by someone whose only job is the dog, while another person lets the cat choose how close to come. Never carry the cat toward the dog, hold the cat in place for inspection, or let the dog chase even in apparent play during these early weeks.
Keep litter trays and cat food somewhere the dog genuinely cannot reach, because a dog raiding either one creates conflict and an upset stomach in a single move. Supervise all shared time, and separate the animals whenever the house is empty until you have weeks of relaxed evidence, not one good afternoon. Notes on which stage the pair has reached, shared in KinsLe through Family Sharing, stop a visiting relative from helpfully opening every door to let them sort it out themselves.