Background: This study was conducted to investigate the clinical value of microRNA (miR)-212-3p in acute coronary syndrome (ACS) patients. Methods: This study involved 128 ACS patients and 110 patients with coronary arterial atherosclerosis. Real-time fluorescence quantitative polymerase chain reaction was employed to measure serum miR-212-3p levels and assessed its correlation with disease severity. The diagnostic efficacy of miR-212-3p was evaluated through receiver operating characteristic (ROC) curve and logistic regression modeling. Furthermore, Kaplan-Meier and Cox regression analyses were utilized to determine the predictive value of miR-212-3p for the occurrence of major adverse cardiovascular events (MACE). Results: The serum miR-212-3p was elevated in ACS patients, with levels in acute myocardial infarction (AMI) patients being greater than unstable angina pectoris (UAP) patients. Serum miR-212-3p demonstrated considerable diagnostic utility in the identification of ACS patients and in differentiating between AMI and UAP cases. Furthermore, miR-212-3p levels correlated with myocardial injury markers [cardiac troponin I (cTnI), high-sensitivity C-reactive protein (hs-CRP), and creatine kinase-MB (CK-MB)], as well as with coronary artery scores (Gensini and SYNTAX). Elevated levels of miR-212-3p were associated with MACE incidence. Serum miR-212-3p, cTnI, Gensini, and SYNTAX score served as independent risk factors for MACE occurrence, with higher expression of miR-212-3p being linked to a poorer clinical prognosis. Conclusion: Serum miR-212-3p might serve as a non-invasive biomarker for ACS diagnosis and MACE prediction and as a supplementary molecular tool in clinical practice.