High-resolution intracoronary imaging provided relevant insights into the field of pathophysiology of acute coronary syndromes (ACS). Human autopsy studies have shown that endothelial erosion may lead to intravascular thrombosis and acute myocardial infarction. We report the case of a 51-year-old woman presenting with ST-segment elevation ACS. In this patient, frequency domain optical coherence tomography (FD-OCT) was performed into the infarct-related artery, showing in-vivo findings suggestive of endothelial erosion, associated with no flow-obstructing luminal thrombus. In this rare case, endothelial erosion, and subsequent thrombosis, in the proximal third of the artery has probably caused embolization and thrombotic occlusion in the mid third. FD-OCT allowed us to obtain a rare in-vivo image of endothelial erosion, providing relevant insights into the setting of ACS.