We present a patient who was diagnosed with hypothermia in the emergency department and the changes in bedside transcranial Doppler (TCD) measurements during and immediately after the diagnoses were recorded. To the best of our knowledge, this is the first case report in the literature in which TCD data were shared in an accidental hypothermia patient in the emergency department. A 78-year-old male patient was brought to the emergency department with the complaint of speech impairment. The respiratory rate was 24 bpm, pulse rate 40 bpm, body temperature 25.6 degrees C, blood pressure 80/50 mmHg, and glasgow coma scale 11. On electrocardiography, sinus bradycardia (40 bpm) and a small deflection (J wave) at the end of the QRS complex were observed. Immediately after the patient's admission, right middle cerebral artery end diastolic velocity (EDV) was 13.42 cm/s, peak systolic velocity (PSV) was 40.25 cm/s, and pulsatile index (PI) was 1.26 cm/s. After 1 hour, her body temperature was 34.5 degrees C. Measurements with TCD were repeated 1 hour later at the same point and EDV was found to be 26.12 cm/s, PSV 84.02 cm/s, and PI 1.33. At the fourth hour, the patient's body temperature was 36.4 degrees C, he was normothermic, and his mental status completely normalized. The patient was hospitalized for follow-up and treatment. This case supports that it can be used in the evaluation of cerebral perfusion and improvement during treatment in patients with accidental hypothermia in their admission to the emergency department.