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How to Stop Other Cats Coming Through a Cat Door
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How to Stop Other Cats Coming Through a Cat Door
Start with the honest bit: a standard cat door cannot tell one cat from another. It's a flap on a hinge — it opens for whatever pushes it. So what actually works to stop other cats coming through isn't a smarter flap. It's controlling when the door is open, what the intruder is coming for, and how they get to it. Done properly, that usually settles it inside a week.
If a neighbourhood cat has started coming in, you'll recognise the pattern. Food disappearing. Your own cat suddenly hiding, or refusing to use the door at all. Then, often, spraying indoors — which is usually the point at which people go looking for answers.
It rarely resolves on its own. An intruding cat that finds food and no resistance simply adds your house to its round.
What your existing door can already do
Every Pet-Tek door has a four-way lock as standard — not as a paid upgrade. Turning the dial gives you four settings:
| Setting | What it does | When to use it |
|---|---|---|
| Fully open | In and out freely | Daytime, when you're home |
| In only | Your cat can come home, but not go back out | Late afternoon, to bring them in before dark |
| Out only | They can leave, but not return through the flap | Rarely useful for this problem |
| Locked | Nothing passes either way | Overnight, and while the house is empty |
"In only" is the setting most people never use, and it's the one that matters here. Almost all intruder visits happen overnight or when the house is quiet. Setting the door to in-only in the late afternoon, then locked once your cat is home, removes the intruder's window entirely — without shutting your own cat out.
Move the food. This is the one people skip.
An intruding cat is almost always coming for food. If the bowl is visible from the door, the door is worth pushing on. If it isn't, most cats stop bothering within days.
- Move feeding well away from the door — a different room entirely if you can.
- Feed at set times rather than leaving a bowl down. Free-feeding is what makes a house worth raiding.
- Lift the bowl at night. Nothing to find, nothing to come back for.
This costs nothing and does more than any hardware change.
Make the approach less inviting
Cats are cautious about routes they can't see along. An intruder that has to cross open ground, or squeeze past something, will usually pick an easier house.
- Clear the run-up to the door — move the planter, bin or chair that gives cover.
- A door set into glass is exposed and well lit, which intruders dislike far more than a shadowed corner in a timber door.
- Motion-triggered garden lighting near the approach is often enough on its own.
Check your council's cat rules while you're at it
Many Australian councils have rules about cats being kept to the property — some overnight, some around the clock — and a number have been tightening them. The detail varies council to council, so the only reliable answer is your own council's.
It's worth knowing for two reasons. If you're required to contain your cat anyway, a permanently open door isn't an option — so the locking schedule stops being a workaround and becomes simply how you run the door. And containment cuts both ways: as more neighbours keep their cats in, the intruder problem shrinks on its own.
What about possums?
Possums are the other uninvited guest, and they behave differently to cats — persistent, strong, and after the same food bowl.
The approach is the same but stricter, because a possum won't be put off by an awkward approach the way a cat is:
- Lock the door overnight, without exception. Possums are nocturnal; a locked flap between dusk and dawn ends it.
- Remove all food from the room the door opens into, not just from near the door.
- Check what's above the door — an overhanging branch or a pergola can give roof access straight to it.
Possums are protected native wildlife across Australia. You can exclude them from the house, but trapping or relocating them isn't something to take on yourself — so exclusion is the practical route anyway.
If none of that is enough
If you've locked overnight, moved the food, cleared the approach, and the same cat is still getting in during the day while you're out, you've reached the limit of what a standard flap can do. That isn't a fault in the door — no hinged flap distinguishes between animals, whatever it costs.
At that point it's worth talking it through rather than buying something on spec. Send us the situation — the door you have, the pattern of visits, what you've already tried — and we'll tell you honestly whether anything we make would change it, or whether it's a scheduling problem that needs a different schedule.
Getting the door itself right
One thing that quietly makes all of this harder: a door that's the wrong size, or in the wrong place. A flap that's oversized for your cat is also comfortably sized for the neighbour's tom. If you're replacing rather than adjusting, size it to your own cat rather than buying the biggest that fits — our cat door sizing guide covers how to measure your cat and which flap that points at, and the Find Your Fit tool matches your cat and your doorway to a specific model in about a minute.
If the new door is going into glass, it's worth reading what that costs first — and if the glass is toughened or double glazed, this guide explains why the panel gets replaced rather than drilled. To have it fitted, our installer directory lists independent specialists by region.
The short version
- Set the door to in only in the late afternoon, locked overnight.
- Move the food away from the door, and lift the bowl at night.
- Clear the approach so there's no cover.
- Check your council's cat rules — you may be required to do most of this anyway.
- Give it a week before deciding it hasn't worked.
Common questions
How do I stop other cats coming through my cat door?
Set the door to in-only in the late afternoon and locked overnight, move food away from the door and lift the bowl at night, and clear any cover on the approach. Most intruder visits happen overnight or while the house is empty, so removing that window usually solves it in about a week.
Can a standard cat door tell cats apart?
No. A standard flap is a hinge — it opens for whatever pushes it, and no amount of adjustment changes that. It's the reason the fix is scheduling and food rather than hardware.
What is a four-way lock on a cat door?
A dial that sets the flap to one of four states: fully open, in only, out only, or locked. In-only lets your cat come home without going back out, which is the most useful setting for keeping an intruder cat out overnight.
How do I keep a possum out of my cat door?
Lock the door overnight without exception, since possums are nocturnal, and remove all food from the room the door opens into. Check for an overhanging branch or pergola giving roof access. Possums are protected native wildlife across Australia, so exclusion is the practical approach.
Do Australian councils require cats to be kept inside?
Many councils have rules on it and several have been tightening them, but the detail varies from council to council. Check your own council's cat curfew or cat containment page — it's the only source worth relying on.
Will a smaller cat door keep other cats out?
Not reliably, because a neighbouring cat is often a similar size to your own. Sizing the flap to your cat rather than buying the largest that fits helps at the margins, but the locking schedule is what actually stops an intruder.