Hashimoto’s encephalopathy (HE) is a rare neurologic syndrome that can accompany Hashimoto’s disease or occur independently. The spectrum of symptoms – broad and uncharacteristic – hinders the diagnostic process. Hashimoto’s encephalopathy can resemble every kind of delirium disease and rapidly progressive dementia, which is why the case report presented in the paper is significant for doctors of all specialisations. The majority of patients are in the euthyroid state. The course of the illness may be acute stroke-like or with psychiatric symptoms and epileptic seizures. HE is most often diagnosed by excluding other causes of neurological disorders, and by identifying encephalopathy and high levels of thyroid peroxidase and thyreoglobulin antibodies, which is crucial for a quick and accurate diagnosis. Cerebro-spinal fluid examination and electroencephalography are also very useful. Therapy with steroids is the treatment of choice, however, if no clinical improvement is apparent or resistance to steroids occurs, other methods like plasmapheresis, immunoglobulins, immunosuppression or biological drugs are used. Quick and accurate diagnosis followed by appropriate treatment ensures a promising prognosis.