No — chocolate is toxic to dogs.
Chocolate contains theobromine and caffeine, which dogs metabolize very slowly. Even small amounts can cause vomiting and diarrhea; larger amounts can cause seizures, heart failure, and death. Dark chocolate and cocoa powder are far more dangerous than milk chocolate. Use the chocolate toxicity calculator to check exactly how serious an incident is.
If your dog already ate this, don't wait for symptoms — call your vet now, or the ASPCA Poison Control line at (888) 426-4435. Note what and how much was eaten.
Get the printable list of the 30 most dangerous foods for dogs.