To use neighborhood-level Child Opportunity Index (COI) measures to investigate disparities in congenital heart surgery postoperative outcomes and identify potential targets for intervention. In this single-institution retrospective cohort study, children <18years old who underwent cardiac surgery between 2010 and 2020 were included. Patient-level demographics and neighborhood-level COI were used as predictor variables. COI-a composite US census tract-based score measuring educational, health/environmental, and social/economic opportunities-was dichotomized as lower (<40th percentile) vs higher (≥40th percentile). Cumulative incidence of hospital discharge was compared between groups using death as a competing risk, adjusting for clinical characteristics associated with outcomes. Secondary outcomes included hospital readmission and death within 30days. Among 6247 patients (55% male) with a median age of 0.8years (IQR, 0.2-4.3), 26% had lower COI. Lower COI was associated with longer hospital lengths of stay (adjusted HR, 1.2; 95% CI, 1.1-1.2; P<.001) and an increased risk of death (adjusted OR, 2.0; 95% CI. 1.4-2.8; P<.001), but not hospital readmission (P=.6). At the neighborhood level, lacking health insurance coverage, food/housing insecurity, lower parental literacy and college attainment, and lower socioeconomic status were associated with longer hospital length of stay and increased risk of death. At the patient-level, public insurance (adjusted OR, 1.4; 95% CI, 1.0-2.0; P=.03) and caretaker Spanish language (adjusted OR 2.4; 95% CI, 1.2-4.3; P<.01) were associated with an increased risk of death. Lower COI is associated with longer length of stay and higher early postoperative mortality. Risk factors identified including Spanish language, food/housing insecurity, and parental literacy serve as potential intervention targets.