Quadricuspid aortic valve is an uncommon congenital anomaly that often causes aortic regurgitation in adulthood, necessitating valve replacement. A 54-year-old woman presented with symptoms and signs of aortic regurgitation, but during surgery a quadricuspid aortic valve was identified. The abnormal cusp was fibrotic, short, thick, and fenestrated. Excision of the fourth cusp was performed and valve repair carried out successfully, with only minimal regurgitation.