The case of an 18-year-old adult male killed by a cougar (mountain lion) is presented. Cougars rarely attack humans, but inflict serious injury. Large bite or claw wounds, frequently to the head and neck, require emergency medical management with attention to deep structure injury, as well as potential Pasteurella multocida or rabies infection. Cougar–human interactions are increasing as rural housing developments and recreation in wilderness areas expand. Understanding cougar predator–prey behavior may help prevent attacks and injuries, particularly to children.