Hashimoto encephalopathy (he) is a rare disorder with a great diversity in clinical presentation of neurological and/or psychiatric symptoms. We describe a case of Hashimoto thyroiditis with hypothyroidism and Hashimoto encephalopathy in a fifteen-year-old boy who was referred to a child and adolescent psychiatrist due to a suspicion of a psychotic episode. Patient recovered after treatment with levothyroxine and corticosteroids.