Ectopic atrial tachycardia is an uncommon cause of supraventricular tachycardia in children. It can resolve spontaneously or induce dilated cardiomyopathy. It is important to recognize this entity as a reversible cause of dilated cardiomyopathy, characterized by the presence of an abnormal focus located in the atrial myocardium and distinct to sinus node. Treatment strategies include the use of antiarrhythmic drugs, radiofrequency ablation, and, in patients refractory to medical treatment, surgical resection of the ectopic focus. We describe a patient with dilated cardiomyopathy due to an atrial ectopic focus and its resolution after medical treatment.