We report a case of Diabetic ketoacidosis accompanied byrare complications of severe hypothermia, with development of cardiac arrest and prominent J (Osborn) waves on electrocardiography. A 27-year-old woman with a 14-year history of type 1 diabetes was admitted to hospital with disturbance of consciousness. She had a core temperature of 27.8°C and a serum glucose of show high mg/dL. Twelve-lead electrocardiography showed atrial fibrillation, prominent J (Osborn) waves, and QT prolongation (Fig. 1). She received a 10-unit bolus of regular insulin, followed by intravenous fluids and insulin infusion. Successful rewarming was achieved with an external rewarming blanket and warm intravenous fluids over 24 hours with resolutioned follow-up ECG. Patient discharged from the hospital after an 7-day admission. This case illustrates that rare complications such as hypothermia can occur in diabetic ketoacidosis, with development of cardiac arrest. Prompt recognition of severe hypothermia is critical in DKA because hypothermia may protends a poor prognosis.