A 45-year-old premenopausal woman presented with acute myocardial infarction (MI). An intravascular ultrasound (IVUS) revealed that her distal right coronary artery was occluded by spontaneous coronary artery dissection (SCAD). She did not have any specific condition related to SCAD. At follow-up cardiac catheterization, an acetylcholine provocation test was applied to examine the etiology of SCAD, and definitive coronary vasospasm was induced with chest symptoms and significant electrocardiographic change. A Ca-channel blocker was administered and since then chest pain has subsequently so far been relieved. The current case suggests the significance of the IVUS in detecting etiology of MI in younger patients and the potential association between SCAD and coronary vasospasm.