Instructions
Observe the dog when it is playing to see when it begins to show aggression. A little growling during play is normal, but watch carefully to see if the behavior is escalating into forceful aggression.
Stop the activity immediately when the dog growls. If you are playing tug of war, take the toy away and speaking in a sharp tone, say "No" or whatever command you normally use to discipline the dog.
Stand up if you were in a sitting position; face the dog, but do not engage him. Growling is sometimes a dominance issue in a dog with an "alpha" personality. The object is to establish yourself as the more dominant personality and let it know that you are in control.
Alternatively, take the toy and walk away from the dog to indicate that the play session is over. Use discretion. This may work better with puppies rather than adult dogs. When dealing with an adult dog, avoid turning your back on it when it is overexcited or overly aggressive.
Praise the dog when it calms down. Continue to reward nonaggressive behavior when playing and stopping the play session if the dog resumes growling.
How to Stop a Dog From Growling When Playing
Growling is one of the ways that dogs communicate. When playing a game of tug of war with a toy, growling signifies that they are willing to be aggressive in order to win the game. Some dogs need to be trained to understand when growling is appropriate. A dog should growl when there is imminent danger, but should not get overly excited during play to the point of aggression. A puppy's growl is cute, but an adult dog's growl when playing might indicate that it is ready to bite. This type of aggression should be curbed before it spins out of control.