Tetralogy of Fallot (TOF) is the most common cyanotic congenital heart disease. Only a few patients reach adulthood without surgical correction. Unrepaired TOF patients with mild to moderate right ventricular outflow tract (RVOT) obstruction may be clinically silent until adulthood. TOF with hypoxic spells present as periods of profound cyanosis that occur because of almost total RVOT obstruction. So, hypoxic spell typically occurs in a crying infant but is rare in an adult. In this report, we presented a case of a 75-year-old patient with uncorrected TOF presenting with hypoxic spell, consequent pulmonary hypertension and chronic heart failure. This is the oldest case of natural survivor with uncorrected TOF in Korea and the oldest patient presenting hypoxic spell worldwide.