Coronary microvascular disease (CMVD) is not an uncommon complication after acute myocardial infarction (AMI), independent of prompt revascularization. It is a serious yet underdiagnosed disease that has a major impact on patient outcomes. Even when the infarct-related artery is successfully revascularized, a significant percentage of patients still have compromised microvascular circulation, which is linked to higher cardiovascular mortality and hospitalization for heart failure. The well-known invasive methods, such as the index of microvascular resistance (IMR) and the coronary flow reserve (CFR), have been considered as gold standards. However, they are constrained by their hazards and complexity. Non-invasive techniques, such as echocardiography Doppler for CFR assessment, positron emission tomography (PET), cardiac magnetic resonance imaging (CMR), and some other techniques provide alternatives, but their accessibility, cost and implementation during the peri-AMI period raise obstacles to their wider use. This review highlights both invasive and non-invasive modalities as it examines the diagnostic methods and prognostic significance of CMVD development early after AMI. Enhancing long-term results in this high-risk population requires a thorough understanding of pathophysiology and a commitment to larger diagnostic and prognostic studies for CMVD.