A 39-year-old man exhibiting unstable angina was admitted to our hospital, and urgent coronary angiography revealed stenosis of the proximal left anterior descending coronary artery (LAD). A drug eluting stent was implanted at this site, and the patient was discharged uneventfully on the 3rd hospital day. Optical frequency-domain imaging (OFDI) was successful in detecting an intra-plaque hematoma, minor intimal disruption, and thrombus at the culprit lesion in this patient. These observations suggest that this hematoma might be the result of subsequent blood filling into the ruptured plaque through this minor intimal disruption.