A quadricuspid aortic valve is a rare congenital anomaly whose diagnosis is mostly incidental.The overall incidence in the population is less than 0.00033% in autopsies and less than 0.0065% in transthoracic echocardiography.Most patients present with valvular disorders, with the most prominent being aortic regurgitation.The following case report presents a 60-year-old female patient with severe aortic insufficiency.Her symptoms progressed rapidly, and she had a clear indication for valvular replacement.Preoperative transthoracic and transesophageal echocardiography showed no evidence of a fourth aortic cusp.However, during the surgical procedure, a native quadricuspid aortic valve was found.The native aortic valve was exchanged for a biological prosthetic valve.Postoperative echocardiography showed a normal functioning prosthetic aortic valve.A quadricuspid aortic valve is a rare anatomic variation that can result in aortic regurgitation due to mechanical valvular abnormalities.