Myocardial infarction without angiographic moderate to severe stenosis (> 50%) and any other related diagnosis on clinical presentation is defined as myocardial infarction with nonobstructive coronary arteries (MINOCA). Common causes of MINOCA working diagnosis includes plaque disruption, spontaneous coronary artery dissection, coronary artery spasm, coronary thromboembolism, Takotsubo cardiomyopathy, and myocarditis. Clinical history, assay of myocardial enzymes, electrocardiogram, echocardiography, coronary angiography, and left ventriculography facilitate the initial diagnosis of MINOCA and reveal the underlying causes, while cardiovascular magnetic resonance and optical coherence tomography (OCT) are used to confirm the diagnosis. Although cardiovascular magnetic resonance is the gold standard noninvasive diagnostic tool for MINOCA, its ability to diagnose the cause and mechanism underlying this condition in the coronary arteries is limited because of its image resolution. Observational studies have demonstrated that OCT can be used to determine the underlying cause of MINOCA by investigating the characteristics of the culprit lesions and to predict the prognosis of the patients. In this article, we review the current diagnostic approach for MINOCA focusing on each imaging tool. Furthermore, we reevaluate the role of OCT in the clinical management of MINOCA. Identifying the cause of MINOCA through OCT might help select optimal and effective drug treatments and improve prognosis.