Abstract Aim This study developed a nomogram to predict the risk of ischemic mitral regurgitation (IMR) after percutaneous coronary intervention (PCI) in patients with ST-segment elevation myocardial infarction (STEMI) patients and evaluate their long-term prognosis. Methods Data from 342 STEMI patients were collected. Logistic regression identified independent risk factors for IMR during hospitalization, while Cox regression assessed risk factors during follow-up. The nomogram was developed based on these factors. ROC evaluated its predictive value, and decision curve analysis/clinical impact curves assessed clinical utility. Kaplan–Meier analysis evaluated the model's prognostic value. Results The independent risk factors for hospitalized IMR after PCI in STEMI patients included Gensini score (OR 1.009; P = 0.047), left ventricular ejection fraction (LVEF) (OR 0.941; P = 0.007), albumin (OR 0.941; P = 0.046), and systemic immune-inflammatory index (SII) (OR 1.096; P