A 25-year-old young man was admitted with typical manifestations of acute myocardial infarction. Cardiac catheterization performed 2 weeks later showed a left ventricular aneurysm and normal coronary arteries. Because of the unusual clinical features, an endomyocardial biopsy was done and revealed histopathological changes of acute myocarditis. Acute myocarditis presenting as acute myocardial infarction with left ventricular aneurysm formation at the same time was never reported before. The long-term prognosis of the patient with left ventricular aneurysm caused by myocarditis still needs further observation.