We herein report a case of intramural hematoma without ongoing myocardial ischemia that healed spontaneously with conservative treatment. A 37-year-old woman was admitted due to chest pain. Acute coronary syndrome was diagnosed by electrocardiography and echocardiography. Coronary angiography showed 90% stenosis in the distal portion of the left anterior descending coronary artery, where intravascular ultrasound showed a hematoma, but optical coherence tomography could not detect the entry point. Therefore, we identified the intramural hematoma as the etiology. Because the coronary flow was maintained and chest pain disappeared, we chose conservative treatment. Fifteen days after admission, coronary computed tomography showed an improvement in the intramural hematoma.