Heat stroke is a life-threatening condition requiring immediate initiation of rapid and effective cooling. We report successful cooling with initial intravascular cooling use that rapidly achieved the target temperature with continued normothermia thereafter. A 39-year-old previously healthy man collapsed on a hot, humid day and presented with a disturbance of consciousness. On initial examination, Glasgow Coma Scale score was 6/15, and his body temperature was 40.7°C. He was therefore intubated, and fluid resuscitation was initiated. A Cool Line catheter (Asahi KASEI ZOLL Medical, Tokyo, Japan) was inserted, and aggressive cooling was started using the intravascular balloon-catheter system (The Thermogard XP system; Asahi KASEI ZOLL Medical) within 32 minutes of arrival. His core temperature reached 38.8°C after 17 minutes of intravascular cooling at an average cooling rate of 0.10°C/min. Further investigation revealed impaired liver function and renal failure. His hemodynamic condition was stabilized, and no vasoactive agents were administrated during hospitalization. The cooling catheter was removed on day 2 of admission, and no bleeding, infection, or thrombosis associated with catheter placement was observed. Blood and urine cultures remained negative. Extubation was performed on day 3, and he was discharged on day 5 without further complication or sequelae. It is essential in the treatment of heat stroke to cool as quickly as possible and to provide cardiovascular support. In patients with severe heat stroke and multiple-organ dysfunction, initial use of the active intravascular cooling technique is warranted for aggressive cooling.