Cases of coronary arteries with anomalous aortic origin are rare. An isolated single coronary artery is a congenital anomaly occurring in approximately 0.024-0.066% of the population. Atherosclerosis of these arteries is not infrequent with potentially severe consequences, but interventional procedures are rarely performed. We report an acute coronary syndrome case due to a subtotal paraostial left anterior descending (LAD) occlusion of a single L-I type coronary artery. Another severe stenosis was also present at mid-LAD. The patient was successfully treated with transradial percutaneous coronary intervention (PCI). Our case shows that when the anatomy is suitable, complex PCI can be performed successfully in single coronary arteries.