Although spinal anesthesia has long been considered a safe technique, it is not without risk or side effect. Cauda equina syndrome is a rare but serious complication of spinal anesthesia. We have experience a case of cauda equina syndrome after spinal anesthesia. A twenty year old healthy male patient complained of pain, numbness, tingling sensation and motor weakness on his right lower extremity 8 hours after subarachnoid blockade. On the following day, the patient was noted to have a right L1 to S2 radiculopathy. Magnetic Resonance Imaging results were unremarkable. The patient sprained his ankle while trying to move down from the bed, so short leg splint was applied. Then he had additional right common peroneal nerve injury from the splint. His neurologic symptoms improved gradually thereafter, and three months postoperatively his electromyogram revealed improving stage from right common peroneal nerve palsy.