Human norovirus (NoV) is the most common viral cause of acute gastroenteritis worldwide. In addition to affecting the digestive system, NoV also affect the neurological systems. A 15-month-old girl presented with vomiting and diarrhea for 2 days, along with one seizure. Her stool was NoV-nucleic-acid-positive, and she had normal results for cerebrospinal fluid (CSF), cranial magnetic resonance imaging, and video-electroencephalography (VEEG). She was initially diagnosed with benign convulsions with mild gastroenteritis, but she subsequently developed walking instability, an involuntary chewing-like movement of the oropharynx, and decreased speech. On rechecking, her CSF result was positive for anti-NMDAR antibody. She was diagnosed with anti-NMDAR encephalitis, treatment consisted of intravenous immunoglobulin and glucocorticoid, following which she almost completely recovered. This case suggests the possibility that NoV infection may be one of the triggers of anti-NMDAR encephalitis. Patients with NoV infections and neurological manifestations should be considered for anti-neuronal antibody testing.