Sinus of Valsalva aneurysm (SVA) is an uncommon cardiac anomaly and can be congenital or acquired. Among these, the left SVA is extremely rare.1) A 36-year-old healthy woman visited the local hospital with acute chest pain. Based on the electrocardiogram (Figure 1; ST elevation in leads I and augmented vector left and ST depression in lead II, III, augmented vector foot and V4-6) and laboratory tests (creatine kinase: 1,155 U/L, creatine kinase-MB: 281 mcg/L, troponin I: 5.3113 mcg/L), acute coronary syndrome was suspected. However, coronary angiography showed that the left coronary artery was compressed by the left SVA (Figure 2A, arrow). On computed tomography, 3.5×3.5 cm sized left SVA was confirmed (Figure 2B and C, arrows) and referred to our hospital for emergent Valve sparing aortic root reimplantation. During the surgery, there was a 1×1 cm sized round opening in the left coronary cusp (Figure 3A, arrow), and a fresh thrombus was observed, suggesting an acute event (Figure 3B, arrow). There were no specific abnormal findings in the genetic or histological examination. The patient discharged uneventfully and is being followed up for heart failure.