Norovirus is an emerging pathogen that causes gastroenteritis outbreaks. Here, we reported an adult female case of norovirus-related encephalitis/encephalopathy (NvREE) with abnormal behaviour, apathy, motor aphasia, bradykinesia and gait disturbance. We treated the patient with intravenous methyl-prednisolone pulse therapy and she recovered quickly. There were slight abnormal signals in the cortex of the opercular part and insula on the MRI fluid-attenuated inversion-recovery (FLAIR) image, generalised slow wave as a background activity in her EEG and cerebrospinal fluid pleocytosis, which restored soon after her recovery. We successfully detected the norovirus genome in stool samples from all seven family members. This is a first case report of an adult NvREE with detection of pathogenic evidence. There could be more cases of NvREE with mild neuropsychiatric symptoms, considering the increasing outbreaks each year.