We report a forensic autopsy case of brain germinoma in a 26-year-old man who was severely wasted and initially suspected of fatal neglect. He had a history of nocturnal wandering and was confined by his parents. Neuropathological examination showed germinoma in the hypothalamus and neurohypophysis. The cause of death was certified as hypothalamo-hypophyseal insufficiency due to germinoma. Because hypothalamic lesions may dysregulate feeding behavior and sleeping rhythms, germinoma was considered the causative lesion of the anorexic wasting and nocturnal wandering. Confinement was a preventive measure of the patient's wandering. The findings in this case indicated that hypothalamic tumors should be recognized as a cause of wasting in autopsies suspected of fatal neglect.