Congenital diverticulum of heart is a rare entity, which may arise from the atria, atrial appendages, coronary sinus or the ventricles. A 3-year-old child presented with history of early fatigability for 6 months and recent upper respiratory tract infection. Chest X-ray and echocardiogram revealed marked right atrial enlargement. At surgery, a right atrial diverticulum was excised under cardiopulmonary bypass. Pathology revealed thickened endocardium with edema and myocardial fiber hypertrophy. Our experience with this rare congenital disease is presented along with a review of the literature.