Cat Spraying Indoors: Why It Happens and How to Stop It

Indoor spraying is one of the more misunderstood cat behaviours. It is not a litter tray problem. It is communication. Here is what your cat is trying to say.

Vet guidance: Some symptoms described in this article may have a medical cause. If your cat is showing sudden behaviour changes, signs of pain, or any change in urination, please contact your vet promptly.

Finding urine on your walls, the back of your sofa, or beside the front door is deeply frustrating. But understanding that spraying is a communication behaviour rather than a toilet failure changes the approach completely.

What is spraying?

Spraying is when a cat deliberately deposits small amounts of urine on vertical surfaces to mark territory. It is a normal feline behaviour, used in the wild to communicate ownership, sexual availability, and health status to other cats via scent. Domestic cats spray for the same reasons: to mark their territory, signal their presence, and manage perceived threats. The problem is that they are doing it inside your home.

How to identify spraying

Classic signs include urine on vertical surfaces such as skirting boards, wall corners, behind furniture, door frames, and inside cupboards near entry points. The amounts are small with a strong scent, not a puddle. You may notice the cat standing with tail raised, sometimes quivering the tail tip. The location is often near windows, cat flaps, or external doors. If you are unsure whether you are seeing spraying or regular urination, the location is usually the clearest indicator. Horizontal surface means urination. Vertical surface means spraying.

Why cats spray indoors

Territorial threat from outside cats

One of the most common drivers of indoor spraying is an unfamiliar cat visible in the garden or through a window. Your cat can smell other cats even if they cannot see them, particularly if a neighbourhood cat is spraying near your back door or cat flap. Your cat responds by marking the boundary on their side. From their perspective, they are doing exactly the right thing.

What helps: block the sight line to the garden temporarily using frosted window film on lower panes. If you have a cat flap, consider switching to a microchip-activated model that will not carry another cat's scent inside.

Multi-cat household tension

When cats in the same home do not have a comfortable relationship, spraying is a common response, particularly from a cat who feels their space is being encroached on. Signs of underlying tension include staring contests, one cat blocking the other's access to food or the litter tray, and one cat staying permanently in one room.

What helps: resource separation through multiple feeding stations, water bowls, litter trays, and beds, more vertical space, and if needed, a managed re-introduction process.

New arrivals in the home

A new cat, dog, baby, or partner can all trigger spraying. The cat's territory has changed through new smells, new dynamics, and new patterns of movement, and they respond by marking more intensively.

Change and instability

More general stress from moving house, building work, or changes in routine can also trigger spraying in cats who are sensitive to change.

Unneutered cats

Unneutered males have the strongest urge to spray as it is deeply tied to sexual behaviour. Unneutered females in heat can also spray. Neutering reduces spraying significantly in most cats, though it does not always eliminate it completely.

How to address indoor spraying

Rule out a medical cause first

Occasionally what looks like spraying is a medical condition causing a cat to urinate in small amounts in unexpected places. If you have never seen your cat do it directly, a vet check to rule out urinary issues is sensible.

Identify the trigger

When did the spraying start? What changed around that time? The closer you can get to the root cause, the more targeted your response can be.

Clean affected areas thoroughly

Enzyme-based cleaners are essential. Standard cleaners do not break down the proteins in cat urine. The smell remains for your cat even if you cannot detect it, which draws them back to the same spot. Look for products labelled enzyme-based or bio-enzymatic at pet shops.

Use pheromone support

Cat calming diffusers can reduce general anxiety and territorial marking. Place them in rooms where spraying has occurred and run them continuously for at least four weeks for the best effect.

Consider neutering if not already done

If your cat is intact, neutering is the most impactful single intervention for spraying driven by reproductive instinct.

Seek behaviourist support for persistent cases

Spraying that continues despite these measures, or that escalates, benefits from professional input. A registered cat behaviourist can identify subtle triggers you might have missed and design a targeted plan.

Related articles

• How to Stop a Cat Spraying: Step by Step
• Cat Peeing Outside the Litter Tray
• Cats Fighting Each Other

Frequently asked questions

Can neutered cats still spray indoors?

Yes. While neutering significantly reduces spraying, particularly in males, it does not eliminate it entirely. Neutered cats of both sexes can spray in response to stress, territorial threat, or conflict with other cats.

How do I tell the difference between spraying and urinating?

Spraying typically happens on vertical surfaces, involves a small amount of strongly-scented urine, and is often accompanied by the cat standing with their tail raised and quivering. Regular urination happens on horizontal surfaces in larger puddles.

What triggers cat spraying?

The most common triggers are a perceived territorial threat from other cats inside or outside the home, changes in household composition, and stress or anxiety. Spraying is the cat's way of marking their territory and making themselves feel more secure.