The short answer: No.
The long answer: Pistachios are not toxic to dogs, but are best avoided for many reasons. Since this type of nut has a hard shell, jagged shape, and small size, your dog might ingest it as a whole. This could lead to choking, throat injury, or intestinal blockage.
Dogs don’t digest nuts well, and eating them on a regular basis or in large quantities in one sitting can cause gastrointestinal distress, obesity, or pancreatitis—possibly due to the high salt or phosphorus content found in them. Plus, pistachios may contain Aspergillus mold which could cause damage to your dog’s liver.
What to do if your dog accidentally eats pistachios: If your dog eats one or two pieces, it shouldn’t be a problem. Just keep an eye on him to make sure he’s okay.
If he consumes a considerable amount of pistachios in one sitting, observe for signs of dehydration, vomiting, diarrhea, and greasy stools. Look out for jaundice, lethargy, liver failure, loss of appetite, and vomiting for possible aflatoxin poisoning caused by the Aspergillus mold. If your dog exhibits any of these symptoms, take him to the vet immediately.
In summary: Refrain from feeding your dog pistachios. You wouldn’t want him to grow fond of this high-protein human snack that can cause his body more harm than good. If you really feel the need to feed him nuts, go for unsalted peanuts, almonds, and cashews served without any shells.