Abstract Introduction: Acyanotic congenital heart disease (ACHD) patients with pulmonary hypertension (PH) are prone to postoperative complications, and characterization of the risk profile continues to fail in identifying inflammatory predilection. Our objective is to investigate the role of platelet-leukocyte indices (neutrophil-lymphocyte ratio [NLR], platelet-lymphocyte ratio [PLR], and systemic immune-inflammation index [SII] [neutrophil × platelet/lymphocyte]) in predicting poor outcomes following cardiac surgery in ACHD cohort with preoperative PH. Methods: This single-center, retrospective risk-predictive study included ACHD patients undergoing surgical correction at our tertiary cardiac center between January 2015 and December 2019. Standard institutional perioperative management protocol was followed, and poor postoperative outcome was defined as ≥ 1 of: low cardiac output syndrome, new-onset renal failure, prolonged mechanical ventilation (MV > 24 hours), stroke, sepsis, and/or death. Results: One hundred eighty patients out of 1,040 (17.3%) presented poor outcome. On univariate analysis, preoperative factors including right ventricular systolic pressure (RVSP) (PH-severity marker), congestive heart failure, albumin, NLR, PLR, SII, and aortic cross-clamping (ACC) and cardiopulmonary bypass (CPB) times predicted poor outcome. However, on multivariate analysis, RVSP, NLR, SII, and ACC and CPB times emerged as independent predictors. An NLR, SII prognostic cutoff of 3.33 and 860.6×103/mm3 was derived (sensitivity: 77.8%, 78.9%; specificity: 91.7%, 82.2%; area under the curve: 0.871, 0.833). NLR and SII values significantly correlated with postoperative MV duration, mean vasoactive-inotropic scores, and length of intensive care unit and hospital stay (P<0.001). Conclusion: Novel parsimonious, reproducible plateletleukocyte indices present the potential of stratifying the risk in congenital cardiac surgical patients with pre-existing PH.