Metronidazole, as a 5-nitroimidazole compound, is effective on anaerobic bacteria and protozoon diseases. Mostly, metronidazole is a tolerable drug but rarely presents serious adverse effects on the nervous system. In case of these adverse effects, treatment must be stopped.In this report, a 3-year-old child hospitalized because of diarrhea is presented. During the metronidazole treatment, loss of sight, vertigo, ataxia, and headache occurred as the adverse effects. By this report, we want to express the rare adverse effects of drugs in the differential diagnoses of nervous system diseases.