Background: Quadricuspid aortic valve (QAV) is a very rare congenital cardiac defect with the incidence of 0.0125%-0.033% (< 0.05%) predominantly causing aortic regurgitation. A certain number of patients (nearly one-half) have abnormal function and often require surgery, commonly in their fifth or sixth decade. QAV usually appears as an isolated anomaly but may also be associated with other cardiac congenital defects. Echocardiography is considered the main diagnostic method although more and more importance is given to computed tomography (CT) and magnetic resonance imaging (MRI) as complementary methods. ----- Case summary: A 60-year-old female patient was referred for transthoracic ultrasound of the heart as part of a routine examination in the treatment of arterial hypertension. She did not have any significant symptoms. QAV was confirmed and there were no elements of valve stenosis with moderate aortic regurgitation. At first, it seemed that in the projection of the presumed left coronary cusp, there were two smaller and equally large cusps along with two larger and normally developed cusps. Cardiac CT imaging was performed to obtain an even more precise valve morphology and it showed that the location of the supernumerary cusp is between the right and left coronary cusp, with visible central malcoaptation of the cusps. Also, coronary computed angiography confirmed the right-type of myocardial bridging at the distal segment of the left anterior descending coronary artery. Significant valve dysfunction often occurs in middle-aged patients and results in surgical treatment, therefore, a 1-year transthoracic echocardiogram control examination and follow-up was recommended to our patient. ----- Conclusion: This case highlights the importance of diagnosing QAV since it leads to progressive valve dysfunction and can be associated with other congenital heart defects which is important to detect, emphasizing the role of cardiac CT and MRI.