LEOPARD syndrome (LS) is a rare inherited disease with multiple somatic abnormalities. LS and Noonan syndrome (NS) share many features, including cardiovascular disorders, and PTPN11 gene mutation is commonly reported in both syndromes. We report a 10-year-old male patient who was diagnosed as LS based on typical phenotypes including multiple lentigines, electrocardiographic abnormalities, ocular hypertelorism and deafness. Although the most prevalent cardiovascular abnormalities in LS are pulmonary stenosis and hypertrophic cardiomyopathy, diffuse bilateral dilatation of the coronary arteries was found on angiography in addition to apical hypertrophic cardiomyopathy in the present case. The vessels showed slight increases in diameter on angiography conducted at an interval of 6 years. A literature review identified several case reports describing coronary ectasia in patients with NS as well as LS. Considering both syndromes share the mutation of PTPN11 gene, coronary arterial involvement could be related to the gene aberration and should be screened even if the patient shows no symptoms of ischemic heart disease.