Yes — as long as it's xylitol-free.
Plain peanut butter is a dog favorite and perfectly safe — it's great for hiding pills. The one critical check: read the label for xylitol (sometimes called birch sugar), which is lethal to dogs. Stick to natural, unsweetened varieties.
Enjoy — this is a safe treat in sensible portions. Introduce any new food gradually and watch for individual sensitivities, just like with people.
Get the printable list of the 30 most dangerous foods for dogs.