Psychotic symptoms and disorders can emerge due to structural brain abnormalities. The septum pellucidum is one of the midline brain structures, which consists of the fusion of two thin membranes. Cavum vergae is recognized as the most severe form of fusion defect in the membranes of septum pellucidum. Although cavum vergea is reported to be common in schizophrenia and other psychotic disorders, a significant relationship has been found only for anomalies greater than 6 mm. Large cavum vergae may be a marker of developmental anomalies in other midline structures and connections, which in turn may lead to psychotic symptoms and disorders. In this case report, we present cavum vergae in a schizophrenia case with a 25 year history of untreated psychosis, discuss the probable relation of psychotic symptoms to structural brain anomaly, and evaluate the treatment course.