Our objective was to examine clinical/electrocardiogram (ECG) predictors and outcomes of arrhythmias beyond 1 year after pediatric heart transplantation (HTx). We performed a retrospective chart review of 94 1-year HTx survivors, 1988–2006. Clinical records identified patients with arrhythmias occurring >1 year after HTx requiring pharmacotherapy, excluding acute rejection. We reviewed preoperative diagnosis, gender, age at HTx, operative details, transplant coronary artery disease (TCAD), and mortality. We analyzed serial ECGs after HTx for HR, PR, QRS, QT, and QTc intervals. Our results found complete data in 58 patients, 14 (24%) with arrhythmia and 44 controls. Arrhythmias occurred 1.1–17.9 years after HTx (mean = 6.8): 11 focal atrial tachycardia, 1 atrial fibrillation/flutter, 1 atrioventricular node reentry tachycardia; only 1 patient had ventricular tachycardia (VT). Serial ECG intervals were similar between groups, as well as surgical technique, ischemic time, and rejection history. Seven patients (50%) with arrhythmias had death or graft death versus 11% of the controls (P = 0.006). Patients with arrhythmias were more likely to be diagnosed with TCAD (P = 0.007). The patient with VT had no TCAD. In conclusion, supraventricular arrhythmias were frequent (22%) in 1-year survivors of pediatric HTx. These patients were more likely to develop TCAD and/or graft loss/mortality.