Exertional heat stroke (EHS) is the most complicated and dangerous amongst heat injuries that can lead to irreversible injury and even death. Early diagnosis and treatment are therefore crucial determinants of the patient's prognosis. The following case report depicts a soldier who presented primarily with confusion and behavioral changes during physical exercise and later lost consciousness. He was misdiagnosed by the field physician as suffering from supraventricular tachycardia, was treated as such and only diagnosed as suffering from EHS later in the emergency room. Our main aims are: to highlight the possibility of misdiagnosis of EHS even among trained physicians, to describe the main symptoms of EHS, and to emphasize the importance of early diagnosis and proper treatment.