Yes it is. I'd have the dog checked out at the vet. Is he acting ok?
Pistachios contain high amounts of phosphorus which can cause bladder stones in dogs. The pistachios may also contain poisonous aflatoxin (which is a fungus or mold)Low levels are safe for human consumption but dogs are more sensitive and is extremely poisonous to them. http://www.answerbag.com/q_view/476041