A healthy, 34-year-old primigravida at 41 weeks gestational age presented for cesarean delivery due to a category 2 fetal heart tracing remote from delivery. After completion of the surgery under epidural anesthesia, bilateral quadratus lumborum blocks were performed for postoperative pain. Approximately 4 hours later, the patient developed left-sided arm weakness, left miosis, and ptosis. These symptoms resolved within 24 hours. Considering the time course of her symptoms, we believe that the quadratus lumborum block was the likely culprit.