Methylene blue is the first-choice treatment of methemoglobinemia, but it is not readily available in most Korean emergency departments because of an import suspension. An 84-year-old woman with dapsone-induced massive methemoglobinemia visited our emergency department for unclear mentality and cyanosis. Because methylene blue was not available, we intravenously administrated vitamin C (VC) for symptomatic methemoglobinemia, although VC is not a universally accepted treatment. Vitamin C (10 g intravenously) administered 6 hourly successfully treated the dapsone-induced methemoglobinemia and did not adversely affect renal functions. Thus, we recommend that if methylene blue is unavailable, 6 hourly intravenous administrations of 10 g of VC should be considered for dapsone-induced methemoglobinemia.