Objective: To investigate the lipoprotein(a) [Lp(a)] to prealbumin (PA) ratio and the N-terminal pro-brain natriuretic peptide (NT-proBNP) to left ventricular ejection fraction (LVEF) ratio for the prediction of major adverse cardiovascular events (MACE) in patients with acute coronary syndrome (ACS) after percutaneous coronary intervention (PCI). Methods: A 1:1 matched case-control study was performed to retrospectively analyze ACS patients who underwent PCI from January 2022 to June 2022. Patients with MACE were selected as the case group (n = 55), and age- and gender-matched patients without MACE were selected as the control group (n = 55). Clinical data for the two groups was compared by univariate and multivariate logistic regression analysis. Risk factors and the odds ratio (OR) for MACE in ACS patients were evaluated, and receiver operating characteristic curve (ROC) were used to evaluate the Lp(a)/PA ratio, the NT-proBNP/LVEF ratio, and their combination for the prediction of MACE in ACS patients. Results: The MACE and non-MACE groups showed statistically significant differences for time from onset to PCI, LVEF, NT-proBNP, white blood cell (WBC), Lp(a), PA, Lp(a)/PA, NT-proBNP/LVEF, number of catheterizations, number of implanted stents >2, and support diameter >3 (p < 0.05). Multivariate logistic regression analysis showed that LVEF, Lp(a)/PA and NT-proBNP/LVEF were independent risk factors for MACE. ROC curve analysis for Lp(a)/PA showed that the area under the curve (AUC) for the prediction of MACE was 0.779 (0.693–0.864), the cut-off point was 1.36, the sensitivity was 69.1%, and the specificity was 74.5%. The AUC for NT-proBNP/LVEF in predicting MACE was 0.827 (0.75–0.904), the cut-off point was 61.04, the sensitivity was 65.5%, and the specificity was 92.7%. For the combination of Lp(a)/PA and NT-proBNP/LVEF, the AUC for the prediction of MACE was 0.889 (0.830–0.947), the cut-off point was 0.37, the sensitivity was 81.8%, and the specificity was 81.8%. Conclusion: The combination of Lp(a)/PA and NT-proBNP/LVEF at admission showed good predictive value for the occurrence of MACE in ACS patients after PCI.