Atrial aneurysms involving the free wall or atrial appendage are very rare intracardiac anomalies, less than 100 case reported worldwide. It is usually detected by chance and also could be associated with atrial arrhythmias or systemic embolism. Transthoracic echocardiography and cardiac MRI is the standard diagnostic modality. Aneurysmectomy is usually recommended especially in symptomatic cases. We review the literature and report a case of atrial appendiceal aneurysm, a 23 year-old young man whose diagnosis was established with transthoracic echocardiography and cardiac CT angiography.