A 2-year-old, spayed female dog with the chief concern of repeated aggression to strange person at owner’s dock and house was presented to the Animal Behavior Clinic at the College of Veterinary Medicine at Cornell University. Based on the questionnaire and interview about dog, territorial aggression was diagnosed. Behavior modification protocols (protocol for deference; protocol for relaxation; ignore unwanted behaviors; reward relaxed behaviors; using Promise collar; avoid all situations that elicit aggression) were recommended. After 6 months from the first consulting, aggressive behaviors of the dog were alleviated.