Menstrual psychosis (MP) is a condition that is associated with the menstrual cycle and can cause significant mental changes. Information about diagnosis and treatment approaches is limited. MP, which is generally reported to occur in young women around the age of 16, typically has an acute onset consistent with the premenstrual cycle, with short-term psychotic symptoms, and a clinical appearance that ends within a few days of discontinuation of menstruation bleeding. In addition to psychotic symptoms, patients may have significant mood symptoms.In this study, a 42-year-old female patient presented to the psychiatry outpatient clinic with complaints of suspicion of people, thinking that she would see them evil, inability to focus, attention, lack of willingness and insomnia. The patient reported that these symptoms occur in almost every premenstrual period starting from adolescence. Unlike other studies, our case is in adult age and it is noteworthy that she was late diagnosed for MP symptoms since menarche.