Why?
Like other tree nuts, walnuts are very high in fat: in larger amounts, they cause vomiting and diarrhea and may contribute to pancreatitis. When they go moldy, especially nuts that have fallen to the ground, they can harbor molds that produce tremorgenic mycotoxins, which cause tremors and seizures, as documented in dogs. A piece of walnut or shell can also be a choking hazard.
How much?
No walnuts for your cat, fresh, dried, or baked into cakes or salads. If your cat goes outside, pick up fallen walnuts in your yard.
The risks
- Vomiting, diarrhea
- Possible pancreatitis after a large amount
- Moldy walnuts: tremors, seizures
- Choking or intestinal blockage from shells
Your cat ate some: what now?
A small piece of fresh walnut usually isn't serious: watch for vomiting and diarrhea over 24 to 48 hours. If the walnut was moldy, your cat ate several, or they're trembling, wobbly or having trouble breathing, call your vet right away.
Better options
For something crunchy, choose cat treats. A small piece of plain cooked meat or fish will please your cat far more than a walnut.
Common questions
What about black walnuts or walnuts from the yard?
Fallen walnuts, black walnuts included, often go moldy, and those molds can produce toxins that cause tremors and seizures. If your cat chewed on one, call your vet even if they seem fine.
Can cats eat banana bread with walnuts?
Best not. On top of the nuts, it brings sugar and butter, and some recipes add raisins, which are toxic to cats. A crumb on the floor isn't a problem, but don't share your slice.
This information is general and does not replace advice from a veterinarian. If your cat has swallowed something toxic, call your vet or an animal poison control center right away, without waiting for symptoms.