BACKGROUND: Heart failure with preserved ejection fraction (HFpEF) is a common yet under-recognized complication following acute myocardial infarction (AMI), particularly after primary percutaneous coronary intervention (PCI). Early identification of at-risk patients remains a clinical challenge. METHODS: We retrospectively analyzed 458 first-episode AMI patients who underwent emergency PCI at a single center. Patients were stratified into HFpEF (n = 107) and non-heart failure (non-HF) (n = 351) groups based on the 2021 European Society of Cardiology diagnostic criteria. Clinical variables, laboratory markers, echocardiographic parameters, and coronary angiography findings were compared. Logistic regression identified independent predictors of HFpEF, and a predictive model-the Heart Failure with Preserved Ejection Fraction-Acute Myocardial Infarction Score (HFpEF-AMI Score)-was developed and evaluated. RESULTS: Among 458 first-episode AMI patients undergoing emergency PCI, 107 (23.4%) developed HFpEF during hospitalization. Multivariate logistic regression identified four independent predictors of HFpEF after PCI: elevated D-dimer (>184.3 ng/mL; odds ratio [OR] 1.626, 95% confidence interval [CI] 1.466-2.771, p < 0.001), peak N-terminal pro-B-type natriuretic peptide (NT-proBNP) (>2640.11 pg/mL; OR 3.391, 95% CI 2.030-5.273, p < 0.001), increased left ventricular mass index (LVMI) (>105.91 g/m²; OR 2.057, 95% CI 1.152-3.833, p = 0.012), and involvement of the left anterior descending artery (LAD) as the infarct-related artery (IRA) (OR 4.737, 95% CI 2.363-10.545, p < 0.001). Using receiver operating characteristic (ROC) analysis, the HFpEF-AMI Score integrating these four predictors demonstrated excellent discriminatory performance, with an area under the curve (AUC) of 0.882 (95% CI: 0.849-0.910). At an optimal cut-off logit(P) ≥ 0.322, the model achieved a sensitivity of 74.8% and specificity of 86.6%. During 2-year follow-up, HFpEF patients had significantly higher rates of major adverse cardiovascular and cerebrovascular events (MACCE: 19.6% vs. 6.0%) and heart failure-related rehospitalizations (18.7% vs. 4.3%; both p < 0.001). CONCLUSION: The HFpEF-AMI Score is a novel and clinically applicable tool for early identification of patients at risk of developing HFpEF after AMI. Incorporating routine laboratory and angiographic parameters, this score may assist in risk stratification and long-term prognostic assessment.