Acute myocardial infarction in the adolescence is unusual. Moreover, the prevalence of left main coronary artery stenosis is rare in this population. We describe a case of acute ST elevation myocardial infarction in an 18 year-old male. He did not have history of congenital heart disease or other traditional risk factors for premature coronary disease. He was mildy overweight and showed normal laboratory tests except low high-density lipoprotein cholesterol level and modestly elevated plasma homocysteine level. Coronary angiography revealed totally occluded left anterior descending artery and thrombus at the bifurcation of left main coronary artery. He underwent emergency coronary stenting at distal left main coronary artery and proximal left anterior descending artery. He was discharged without in-hospital cardiac event.