Isolated congenital coronary artery fistula (CAF) is rare and varies with respect to size and hemodynamic significance. The prevalence of coronary artery ectasia in association with isolated congenital CAF, regardless of size, and after closure of large fistulae has not been systematically evaluated in the literature. This study aimed to characterize the demographic and echocardiographic differences between patients with large and small fistulae and to describe outcomes with respect to coronary ectasia in those who underwent closure. This is a retrospective review of an echocardiographic database that identified patients coded for CAF (1995 to 2012) and excluded those associated with complex cardiac disease and/or coronary anomalies and cardiomyopathy. Small fistulae were noted to arise mostly from the left anterior descending artery, drain into the pulmonary artery, and have a very low incidence of ectasia (n = 3 of 92), with a mean coronary artery diameter z score in these 3 patients of 3.45 ± 1.15. Larger fistulae had a female predominance, with most originating from the right coronary artery and draining into the right atrium; among the 12 patients who underwent procedural closure of large CAF, all feeding coronary arteries remained ectatic after closure, with a mean coronary artery diameter z score of 9.54 ± 5.66 after a total mean follow-up time of 3.95 ± 4.07 years. In conclusion, the occurrence of coronary dilatation justifies long-term follow-up irrespective of fistula size and successful closure of large CAF.