Graves disease is the most common cause of hyperthyroidism. Patients with Graves disease frequently manifest various psychiatric disorders however, very few reports have described psychotic disorders due to this disease. We report the case of a 42-year-old man with no prior psychiatric or thyroid dysfunction history, presenting apparent psychotic symptoms consisting of delusional ideas of persecution and a delusion of reference with a hallucinatory mechanism. A thyroid test is systematically requested, and fortuitous hyperthyroidism is discovered, followed by cervical ultrasound and autoimmune tests, which confirmed the diagnosis of Graves disease.