Are Walnuts Poisonous to Dogs?

The toxic compounds in walnuts:

• Tremorgenic mycotoxins (e.g., Penitrem A, roquefortine) produced by mold on damp/old nuts and hulls
• High fat/oil content (pancreatitis and GI upset risk)
• Juglone (present in black walnut; main toxicity in horses, less significant in dogs but present in tree/hulls)

If your dog ate walnuts, watch for:

• •Tremors
• •Seizures
• •Incoordination (from ingesting shavings/wood)
• •Vomiting
• •Diarrhea
• •Pancreatitis (from high fat content)

Are all walnuts dangerous to dogs, or just black walnuts?

Black walnuts (Juglans nigra) are listed by the ASPCA as toxic to dogs, with moldy nuts and hulls causing tremors and seizures and wood shavings causing incoordination. English/common walnuts are not a safe treat either: the ASPCA groups walnuts with other nuts as high in oils and fats that can cause vomiting, diarrhea, and potentially pancreatitis, and any walnut can grow mold that produces seizure-causing tremorgenic mycotoxins. Avoid feeding dogs any walnuts.

Why are moldy walnuts especially dangerous?

Walnuts that are damp, old, or fallen on the ground readily grow mold that produces tremorgenic mycotoxins such as Penitrem A. Within hours of ingestion a dog can develop muscle tremors, incoordination, high body temperature, and seizures. This is a veterinary emergency, so keep dogs away from walnuts and walnut trees, especially fallen nuts and hulls.

My dog ate a couple of plain walnuts — what should I watch for?

Watch for vomiting, diarrhea, lethargy, abdominal pain (signs of GI upset or pancreatitis from the fat), and especially neurological signs like tremors, wobbliness, or seizures, which suggest mold toxin exposure. Whole walnuts and shells can also cause choking or intestinal obstruction. Call your veterinarian or the ASPCA Animal Poison Control Center at (888) 426-4435 if you have any concern.

• ASPCA Toxic and Non-Toxic Plants: Black Walnut
• ASPCA People Foods to Avoid Feeding Your Pets

Last updated 2026-06-25