Left atrial appendage aneurysm is a rare cardiac anomaly. It can be congenital in origin or acquired secondary to inflammatory or degenerative processes. As it may cause potentially lethal arrhythmias or thrombi, surgical treatment is needed immediately after the diagnosis. In this article, we report a case of an asymptomatic three-year-old boy with a congenital left atrial appendage aneurysm. The patient was successfully treated with surgical resection of the aneurysm.