Hypoglycemic brain injury is usually reversible, and partial recovery or mortality depends on the affected area. Diffusion-weighted imaging (DWI) may be useful in predicting the prognosis according to the site of involvement. Isolated lesions of the splenium of corpus callosum (SCC) in hypoglycemic brain injury are very rare, and DWI findings of a reversible lesion of the SCC due to deep hypoglycemia associated with sulfonylurea intoxication has been reported only once in the literature. We report the case of a 15-year-old girl admitted to the emergency department who had attempted suicide using sulfonylurea and subsequently went into a coma. The patient had no known previous disease. Except for a blood glucose level of 10 mg/dl, all other blood laboratory tests were normal. DWI performed two hours after admission showed diffusion restriction in the SCC. After receiving treatment for 24 hours, the patient became conscious, and her blood glucose level returned to normal. Two days later, complete resolution of the SCC lesion was revealed by control DWI. We discuss both the DWI findings of the reversible SCC lesion due to hypoglycemic brain injury resulting from sulfonylurea intoxication and the role of DWI in predicting the clinical outcome.