Coronary artery fistula (CAF) is a rare congenital anomaly of the coronary arteries in which abnormal connections are present between the coronary artery branch and the cardiac chambers or a major vessel. The incidence of CAF is estimated at 1 in 50,000 live births, and it is detected in approximately 0.2% of the adult population during coronary angiography. Reports of the coincidence of mitral stenosis and CAF are rare in the literature. We report a case of CAF and mitral valve stenosis in a patient with dyspnea and fatigue before valve replacement and surgical radiofrequency ablation. Coronary angiography showed a connection between the right coronary artery and right atrium. A fistula opening into the right atrium is rare in patients with coronary artery anomalies and mitral valve disease. Coronary angiography of the patient 1 month after surgical repair showed that the coronary anatomy was normal and the fistula was occluded. CAF can be diagnosed more frequently if coronary angiography is performed simultaneously with cardiac catheterization to evaluate valve functions or nonatherosclerotic myocardial ischemia in each valvular heart disease case. Surgical repair of CAF is the first-choice treatment to prevent complications and improve quality of life.