Coronary artery anomalies are rare and usually benign. They are detected by coronary angiograms during invasive catheterization. Single coronary artery anomaly, with the left main artery originating from the proximal right coronary artery, can be responsible for myocardial blood supply insufficiency and causes chest pain or sudden death, especially during physical exercise, as it courses between the aorta and the pulmonary artery. We report a case of a fortuitous diagnosis of single coronary artery anomaly discovered during coronary angiogram and investigated in addition with magnetic resonance angiography. Magnetic resonance imaging can provide a precise description of the coronary artery anomaly and its course between great arteries, allowing accurate surgical planning.