On August 22, 2019, several cloud-to-ground currents struck the top of the popular hiking mountain Giewont (Tatra Mountains, Poland). At the scene, first aid and evacuation were provided by mountain emergency rescue services. The injured patients received care and were initially stabilized at a local general hospital. Some of the victims were then relocated to other nearby hospitals, regional trauma centers, or regional burn centers. This study is a retrospective analysis of regional health system response. The official records of the disaster response from the institutions involved were examined. Surveys were conducted through interviews with mountain rescuers, coordinators, and other health care workers regarding interventions, triage, and communication during the disaster response. The analysis was conducted in accordance with the guidelines of the Medical Commission of the International Commission for Alpine Rescue (ICAR-MEDCOM). There were 134 people involved in accidents: four died at the scene, four were considered severely injured, 118 were moderately and mildly injured, and eight had no signs of injury. Mountain rescue services were able to evacuate and provide first aid to all victims within four hours after activation. Close cooperation among various institutions involved, including mountain emergency rescue services, hospitals, fire departments, dispatch centers, and Helicopter Emergency Medical Services (HEMS), is critical to the successful management of mass-casualty incidents (MCIs) in mountain areas. Effective triage algorithms and communication structures should be implemented.