Most nuts aren’t acutely poisonous to cats, but several pose real dangers through toxicity, mold contamination, high fat content, or added ingredients. Macadamia nuts and black walnuts are the most commonly cited toxic varieties, while other nuts like pecans and regular walnuts can trigger serious digestive problems. Here’s what you need to know about each one.
Macadamia Nuts
Macadamia nuts are the most well-known toxic nut for pets. Most documented cases of macadamia toxicosis involve dogs, where symptoms include hind-limb weakness, vomiting, tremors, fever, and difficulty walking, typically appearing within 12 hours of ingestion. Clinical reports in cats are far rarer, but veterinary toxicologists still classify macadamia nuts as toxic to both species. Because cats are smaller and metabolize substances differently than dogs, even a small amount could cause problems.
The exact compound in macadamia nuts responsible for poisoning hasn’t been identified, which makes it harder to predict how severely any individual cat might react. If your cat eats even one or two macadamia nuts, it’s worth calling your vet or an animal poison control line.
Black Walnuts and Moldy Walnuts
Black walnuts are considered toxic to pets and should be kept away from cats entirely. But with all walnuts, there’s a second risk that’s arguably more dangerous: mold. Walnuts that sit on the ground outdoors or go stale in your pantry are prone to colonization by a fungus called Penicillium crustosum, which produces tremor-causing toxins. In dogs, eating moldy walnuts causes a well-documented syndrome of severe tremors, incoordination, and pain. The same risk applies to cats.
These mold toxins can be present even when walnuts don’t look visibly fuzzy or discolored. A case study found significant concentrations of the toxin on walnut kernels that caused neurological symptoms in an adult human within 12 hours of eating just eight infected kernels. For a cat weighing a fraction of a human’s body weight, far less could be dangerous. If you have walnut trees in your yard, keep fallen nuts cleaned up.
High-Fat Nuts and Pancreatitis Risk
Even nuts that aren’t directly toxic can make your cat seriously ill. Pecans, walnuts, Brazil nuts, and cashews are all extremely high in fat, and cats are not built to handle large amounts of dietary fat at once. The main concern is pancreatitis, a painful and potentially life-threatening condition where the pancreas begins digesting itself after its enzymes activate too early.
Pancreatitis in cats can develop after a single high-fat meal or snack. Symptoms include vomiting, loss of appetite, lethargy, abdominal pain, and sometimes fever. Severe cases can damage surrounding organs and require hospitalization. Fatty foods are one of the known risk factors for triggering a flare-up. Because most nuts pack 50 to 75 percent of their calories from fat, even a handful shared from your snack bowl could be enough to set this off in a small cat.
Seasoned and Salted Nuts
Flavored nuts add another layer of risk. Salt is toxic to cats in surprisingly small amounts. Sodium chloride poisoning can occur at doses starting around 2 to 3 grams per kilogram of body weight, and as little as half a tablespoon of salt can be problematic for a cat over 10 pounds. A smaller cat, under 10 pounds, may show signs of toxicity from even less.
Salted cashews, flavored almonds, and seasoned mixed nuts can deliver a concentrated dose of sodium in just a few pieces. Symptoms of salt toxicity include vomiting, diarrhea, excessive thirst, tremors, and in severe cases, seizures. Garlic and onion powder, common on flavored nut mixes, are independently toxic to cats and can damage red blood cells even in small quantities.
Almonds, Pistachios, and Peanuts
These nuts aren’t classified as toxic to cats, but none of them are truly safe either. Almonds are tough for cats to digest and can cause vomiting or obstruction, especially if swallowed whole. Pistachios carry a high mold risk similar to walnuts, and their shells can be a choking hazard or cause intestinal blockage. Peanuts (technically a legume) are the least concerning of the group, but they’re still fatty enough to cause stomach upset or contribute to pancreatitis.
Plain, unsalted peanut butter in very small amounts is generally tolerated by cats. One concern often raised about peanut butter is the sugar substitute xylitol, which appears in some sugar-free brands and is highly toxic to dogs. The ASPCA has confirmed that cats are not negatively affected by xylitol, so this particular ingredient is less of a worry for feline owners. That said, peanut butter offers no nutritional benefit to cats and the fat content still matters.
Hickory Nuts and Chestnuts
Hickory nuts are listed as non-toxic to cats by the ASPCA. However, their hard shells and large size make them a choking and obstruction risk, and like other tree nuts, they’re high in fat. Chestnuts are similarly non-toxic but can cause digestive upset. Neither belongs in your cat’s diet, even if they won’t cause poisoning in the way macadamia nuts might.
What to Do if Your Cat Eats Nuts
If your cat has eaten a macadamia nut, a black walnut, or any nut that looks or smells moldy, contact your veterinarian right away. For suspected oral poisoning, vets typically induce vomiting as early as possible, then administer activated charcoal to reduce further absorption of the toxin from the gut. Cats are more sensitive to fluid therapy than dogs, so treatment involves careful, incremental fluid support rather than aggressive IV drips. Recovery from mild nut ingestion is usually quick with prompt care, but delays can make things significantly worse.
For non-toxic nuts eaten in small quantities, watch for vomiting, diarrhea, lethargy, or loss of appetite over the next 12 to 24 hours. A single cashew that fell on the floor is unlikely to cause an emergency, but repeated exposure or larger amounts warrant a call to your vet. Cats are obligate carnivores with no nutritional need for nuts of any kind, so the simplest approach is to keep all nuts out of reach.