Objective: To describe a case of renal subcapsular hematoma due to renal endometriosis., Design: Case report., Setting: Departments of Urology and Pathology, Baskent University Faculty of Medicine, Ankara, Turkey., Patient(s): A 46-year-old premenopausal woman was admitted with a left lumbar pain and mass. Ultrasonography and computerized tomography revealed a giant-sized renal subcapsular hematoma., Intervention(s): Computerized tomography, percutaneous drainage catheter placement, surgical exploration, and excision of renal capsule., Main Outcome Measure(s): None., Result(s): Histopathologic examination revealed endometriosis located beneath the fibrous renal capsule., Conclusion(s): Renal capsular endometriosis should be kept in mind among the causes of renal subcapsular hematoma.