How much walnuts for your cat?
Most guides say "a few pieces". Enter your cat's weight and get the actual daily ceiling, worked out from walnuts's calories and the 10%-of-daily-calories treat rule vets use.
Assumes a healthy, neutered adult at a stable weight, and that this is their only treat that day. Puppies, pregnant, very active or unwell pets need different amounts — ask your vet.
Why this verdict for cats
Walnuts pose a choking and fat risk and moldy ones are toxic. They are not suitable for cats.
Walnuts deserve more caution than most nuts, and for a reason unrelated to fat: they are unusually prone to carrying a mould that produces neurotoxins, and one variety is outright toxic to dogs.
How much is safe?
None is the honest answer. Black walnuts are toxic to dogs and are best treated as a poison. English walnuts — the ordinary supermarket kind — are not chemically toxic but are high in fat and among the nuts most likely to develop tremorgenic mycotoxins, which cause seizures. Given that walnuts offer a dog nothing it cannot get elsewhere, there is no case for sharing them.
What happens if a cat eats too much?
Fat-driven vomiting, diarrhoea and pancreatitis at the mild end. Mouldy walnuts — including ones fallen in a garden and left to sit — cause tremors, wobbliness, muscle rigidity, high body temperature and seizures, sometimes within an hour or two. That is an emergency.
How to serve it safely
The practical advice is not to serve them, and to be actively careful in autumn if you have a walnut tree: fallen nuts left on damp ground are exactly where the mould develops. Sweep them up.
🍽️ Feeding it safely?
Frequently asked questions
My dog ate a walnut off the kitchen counter — what now?
A single fresh English walnut is usually a stomach-upset problem rather than an emergency, but call your vet with your dog's weight. If it was a black walnut, or if the nut may have been mouldy or picked up outdoors, go in.
Why are mouldy nuts so dangerous?
They can carry tremorgenic mycotoxins — the same compounds found on mouldy bread and in compost — which act fast on the nervous system and cause tremors and seizures that escalate rather than settle.
More nuts & seeds for cats
By the CanMyPet Editorial Team · Reviewed against ASPCA Animal Poison Control, the American Kennel Club (AKC) and Pet Poison Helpline · Last updated July 31, 2026.
Sources
- ASPCA — People Foods to Avoid Feeding Your Pets
- American Kennel Club — Dog Nutrition
- Pet Poison Helpline — Poison List