Pediatric hypertensive crisis is a potentially life threatening medical emergency, usually secondary to an underlying disease. Hypertension commonly occurs during general anesthesia, and is usually promptly and appropriately treated by anesthesiologists. However in children with severe, unexplained, or refractory hypertension, it has the potential to cause morbidity and even mortality in susceptible patients. We report an anesthetic management of an unexpected hypertensive crisis that developed during general anesthesia in a three-year-old girl with undiagnosed severe left renal artery stenosis.