No, but it should be served in moderation. It is advised to check with your vet before making any changes to your pet's diet.
Peanut butter is considered as one of the "dog-approved” people foods, it's a favorite treat of many canines. Not only is it a good source of protein, but it also contains heart healthy fats, vitamin B, niacin, and vitamin E. Stuff peanut butter into a Kong to keep your dog busy for hours. Choose raw, unsalted peanut butter.
See list of a few “dog-approved” people foods at Cesar's Way.
On the other hand, one of the harmful food for dogs is chocolate. Dark chocolates have always been more toxic than milk chocolates, and these newer chocolates are even more so. Toxic doses of chocolate can cause abnormal heartbeats, kidney failure and death. The toxic dose is dependant on weight, so little dogs are at higher risk, but with the higher levels of cocoa in chocolate products now even bigger dogs are at risk.
Also see Cesar's Way's list of harmful foods for dogs.
Find out how to keep your dog healthy, including tips on feeding and meeting your dog's nutritional needs shared by Pets- WebMD.