IntroductionThe association between hypothyroidism and psychiatric disorders especially psychosis well described in some studies and treatment options of this situation is controversy. The aim of this work is implication the role of early diagnosis and treatment of hypothyroidism with psychotic manifestation. Case Presentation: the patient is 53 years old man was admitted in psychiatric ward because of his jealousy and persecution delusions and some behavioral problems (agitation. Aggression .insomnia and obsessions).he was history of hyperthyroidism 6 month before admission with TSH lower than 0.1 that was treated with radioactive Iodine.6 month after this treatment he referred to psychiatrist with psychosis and behavioral problems that mentioned above and in thyroid function tests his TSH was 57.4 (range: 0.1-5) and T3 and T4 was very lower than normal range. He doesn’t have past history and family history of psychosis or other psychiatric disorders. The patient responded optimally to a combination of levothyroxine (150 microgram daily), haloperidol (15mg daily) and biperidine. He was hospitalized tree times after first admission over two year later with psychosis and in every admission he was thyroid dysfunctions with high TSH (57.4, 19.6, and 32.5) and almost all of symptoms treated with levothyroxine and antipsychotic drugs. Conclusionsthis case shows the importance of ascertaining the thyroid status in patients with psychotic disorders and the need to consider hypothyroidism in the differential diagnosis of new onset psychosis. This case illustrates combination therapy with levothyroxine and antipsychotics are choice option in such situation.