Hashimoto's encephalopathy is an uncommon neuropsychiatric syndrome with varied clinical presentations. It presents as an encephalopathy without central nervous system infection or tumor. Mostly observed ones are seizures, cognitive impairment, movement disorders, altered sensorium, and behavioral and psychotic symptoms. Treatment with steroids and immunosuppressants has led to excellent remission rates. Here, we report a case of a 55-year-old male who presented predominantly with psychiatric symptoms and rapidly progressing dementia. The patient was managed by intravenous steroids and low-dose oral risperidone. Prompt investigations and diagnoses helped in treating the condition. This case highlights that timely diagnosis can lead to an excellent prognosis in this condition.