We present quite a rare case of extracardiac unruptured right sinus of valsalva aneurysm (SVA) complicated with atherothrombosis in a young adult man. A 35-year-old male with a giant unruptured SVA arising from the right coronary sinus (RCS) with extracardiac protrusion was diagnosed by echocardiography. Contrast-enhanced computed tomography (CT) revealed a huge calcified aneurysm with mural thrombi originating from the aortic root, and about 80% stenosis at the initial segment of the right coronary artery (RCA). Intraoperative exploration demonstrated a giant unruptured aneurysm arising from the RCS. Different from other SVAs reported before, this aneurismal wall appeared thick and atheromatous-like. In this aneurysm, there was a small localized intima tearing and mural thrombosis, and the orifice of the RCA was almost blocked. This patient underwent surgical patch repair to prevent aneurysm rupture and coronary artery bypass grafting for RCA revascularization. In conclusion, the pathological examination demonstrated marked foam cells, inflammatory cells, and thrombosis in the aneurismal wall.