Ifosfamide (IFOS) is used in cancer treatment. Ifosfamide-induced encephalopathy (IIE) can result in treatment delay or discontinuation as well as morbidity and mortality. Cases using methylene blue (MB) in acute and prophylactic treatments are discussed. For acute use, marked central nervous system (CNS) improvement occurred within 24h of MB administration. For prophylactic use, the severity of the symptoms decreased significantly compared with previous treatment cycles, and enabled patients to continue further IFOS therapy. MB has potential use in both the acute treatment and prophylaxis of IIE.