The authors present a case report and review the literature on Hashimoto encephalopathy. The onset of the disease may be marked by focal and then progressively generalized seizures or other neurological symptoms, but a cognitive decline or various psychiatric symptoms may also emerge. High levels of anti-thyroid peroxidase antibodies and/or anti-thyroglobulin antibodies are present in the serum. Corticosteroid treatment usually results in an improvement of symptoms. The syndrome is frequently overlooked and, therefore, the authors strongly recommend testing serum thyroid autoantibodies in cases with encephalopathy of unknown origin independently on the presence of thyroid disease in the patient or family history. The importance of long-term immunosuppressive treatment should also be stressed.