An anomalous origin of the left coronary artery from the right sinus of Valsalva (RSV) is rare. We herein report the case of an 80-year-old woman who presented to the emergency department with chest pain. Emergent coronary angiography was performed following a diagnosis of non-ST segment elevation myocardial infarction. A right coronary angiogram showed that the common trunk originating from the RSV branched into the left anterior descending and right coronary arteries. Although the initial angiogram failed to show the left circumflex artery (LCx), considered to be the culprit vessel, computed tomographic angiography demonstrated that the LCx was located immediately below the common trunk and exhibited a retroaortic course. We successfully treated the patient and obtained optimal angiography results.