Williams-Beuren syndrome is a rare familial multisystem disorder occurring in 1 per 20,000 live births. It is characterized by congenital heart defects (CHD), skeletal and renal anomalies, cognitive disorder, social personality disorder and dysmorphic facies. We present a case of Williams syndrome that presented to us with heart murmur and cognitive problem. A 5-year-old girl referred to pediatric cardiologist because of heart murmurs. She had a systolic murmur (2-3/6) in right upper sternal border with radiation to right cervical region. She also had a bulge forehead. Angiography showed mild supra valvular aortic stenosis and mild multiple peripheral pulmonary stenosis. Fluorescent in situ hybridization (FISH) was performed and the result was: 46.XX, ish del (7q11.2) (ELN X1) (7q22 X2) ELN deletion compatible with Williams syndrome. Peripheral pulmonary artery stenosis is associated with Noonan syndrome, Alagille syndrome, Cutis laxa, Ehler-Danlos syndrome, and Silver-Russel syndrome. The patient had peripheral pulmonary artery stenosis, but no other signs of these syndromes were present, and also she had a supravalvular aortic stenosis which was not seen in other syndromes except Williams syndrome. Conclusion. According to primary symptoms, paraclinical and clinical finding such as dysmorphic facies, cognitive disorder and congenital heart defect, Williams syndrome was the first diagnosis. We suggest a more attention for evaluating heart murmur in childhood period, especially when the patient has abnormal facial features or mental problem.