Electrocardiogram showing Wolff-Parkinson-White (WPW) pattern in an asymptomatic patient is common, but it is difficult to assess the potential risk of sudden death in such cases. Although the incidence of sudden death in these patients is extremely low, an interventional approach is suggested for all patients despite its controversial nature. Syncope, despite being induced by various mechanisms, has been considered an alarming sign of sudden death of WPW syndrome. We describe a 16-year-old female patient with an electrocardiogram that demonstrated a WPW pattern combined with unexplained syncope. None of the examinations, including biochemical profiles, brain computed tomography, transthoracic echocardiography, head-up tilt table test and exercise electrocardiogram, clarified her syncope. Consequently, no further electrophysiologic study was performed for this patient. Unfortunately, the patient suffered sudden death while running. The case highlights the need for vigilance when unexplained syncope combined with WPW syndrome. Such cases have high risk of sudden death, and thus, further interventional study and treatment is indicated.