Objectives This study examined the difference in the volume or thickness of the medial temporal lobe between Alzheimer’s disease patients with psychosis (AD+P) and those without psychosis (AD-P). Methods Overall, 31 AD+P patients and 29 AD-P patients were included from the Memory impairment clinics of Pusan National University Hospital in Korea. AD+P was diagnosed according to Jeste and Finkel’s proposed diagnostic criteria for psychosis of Alzheimer’s disease. AD-P included AD patients with no psychotic symptoms during a 5-year follow-up period. Medial temporal volume or thickness was measured by 3-tesla MRI and freesufer analysis. Analysis of variance was used to examine the difference in the volume or thickness of medial temporal lobe between AP+P and AD-P after controlling for age, gender, education years, Clinical Dementia Rating scale-Sum of Box, and total intracranial volume. Results The hippocampal volume in AD+P was smaller than that in AD-P. Conclusion These findings suggest that AD+P is associated with a reduced hippocampal volume.