Coronary artery fistula is a rare congenital cardiac anomaly. We report a 34-year-old woman who presented with a recurrent large pericardial effusion during pregnancy. She was found to have a right coronary artery to coronary sinus fistula. The coronary sinus was severely dilated due to coronary sinus ostial stenosis. Primary surgical closure of coronary artery fistula was performed with resection of coronary sinus ostial stenosis.