A 39-year-old man presented with recurrent lower back and leg pain for 8 months due to repeated hemorrhage into an L5 ligamentum flavum cyst. Lumbar MR imaging showed an extradural cystic mass originating from the ligamentum flavum on the right side in the L5 segment. Microsurgical laminotomy and flavectomy were performed. The symptoms resolved completely and the patient had an uneventful postoperative recovery.