We describe a 59-year-old female with Hashimoto's encephalopathy whose presentation was characterized by a subacute onset of confusion, depressed level of consciousness, tremor and pyramidal signs. She was euthyroid on presentation but antithyroid antibodies were elevated. Hashimoto's thyroiditis was confirmed by thyroid biopsy. There was a spontaneous remission of the neurological disorder. Subacute encephalopathy is often investigated with thyroid function tests only. In cases of unexplained encephalopathy, thyroid antibodies and/or thyroid biopsy should be performed to exclude this condition.