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ST-segment elevation myocardial infarction (STEMI) remains a major cause of cardiovascular mortality and morbidity worldwide. Despite advances in reperfusion therapy, many patients still develop irreversible myocardial injury and adverse ventricular remodeling. Intracoronary mesenchymal stem cell (MSC) administration has been investigated as a potential therapeutic approach, but clinical evidence remains inconsistent. We performed a systematic review and meta-analysis of randomized controlled trials (RCTs) comparing intracoronary MSC administration with standard care in STEMI patients. Databases were searched from inception through February 2026. Eight RCTs involving 796 patients were identified, and seven trials with 400 patients were included in the quantitative analysis after excluding one study under Expression of Concern. MSC administration significantly improved ΔLVEF (I² = 44.6%, p = 0.108; WMD = 3.18, 95% CI: 1.52-4.83, p < 0.001). No significant differences were detected in rehospitalization for heart failure (I² = 0.0%, p = 0.592; RR = 1.14, 95% CI: 0.36-3.61, p = 0.831), all-cause mortality (I² = 0.0%, p = 0.525; RR = 1.51, 95% CI: 0.24-9.31, p = 0.659), or MACE (I² = 0.0%, p = 0.887; RR = 2.47, 95% CI: 0.55-11.05, p = 0.236). Intracoronary MSC administration after STEMI is associated with a modest improvement in left ventricular function, while no reduction in clinical events was found. No major safety signal was identified, although available safety data remain limited. Larger and well-designed trials with longer follow-up are still needed. Trial Registration: PROSPERO: CRD420261286620.