Subvalvular aneurysms are the least common type of left ventricular (LV) aneurysms and can be fatal. Subaortic LV aneurysms are much rarer than submitral LV aneurysms and mostly reported in infancy. They can be congenital or acquired secondary to infections, cardiac surgery or trauma. Here, we report a unique presentation of a large, idiopathic subaortic aneurysm in an adult masquerading as an acute coronary syndrome. Diagnosis was made with the help of a CT aortography. Aneurysm was surgically resected with good results. This case highlights the clinical presentation and management of subaortic aneurysms, an important differential for congenital aortic malformations.