Walnuts — Food safety facts
Do not feed · Dogs · full breakdown on the linked food page
Risk of mould tremorgenic toxins and blockage; the shell can splinter. Avoid entirely.
Short answer
No, walnuts are not safe for dogs and you need veterinary help right away. The shell can splinter and cause a blockage, and mold‑produced tremorgenic toxins are poisonous to dogs. Even shelled walnuts may contain these toxins, so any amount is risky. Watch for vomiting, diarrhea, tremors, or abdominal pain and call your vet or the ASPCA Poison Control Center at 888‑426‑4435 immediately.