Limited data exist regarding outcomes of delayed sternal closure (DSC) in adults with congenital heart disease (ACHD). We reviewed 159 ACHD patients undergoing cardiac surgery 1993-2023, who required DSC (open sternum at the end of operation, n=112) or ESR (sternum emergently reopened, n=47). Regression models were performed to determine factors associated with outcomes. Of 112 patients undergoing DSC, 87 patients (77.6%) underwent DSC ≤4 days, and 25 patients (22.3%) >4 days. The most common operations were valve (n=35, 31.2%), aortic (n=33, 29.4%), and right ventricular outflow tract procedures (n=23, 20.5%). Median time to chest closure was 2 days (interquartile range 1, 5). Apart from gender, baseline characteristics were similar between DSC groups. A stepwise increase in early mortality was observed from DSC≤4 days to DSC>4 days (6.8% vs 32%), as well as incidence of early complications, except sternal infection. Risk factors associated with early mortality were age (p=0.02), DSC >4 days (p<0.001), hemodynamic indication (p=0.03), and single ventricle (p=0.02). On multivariable analysis, lower ejection fraction (p=0.04), hemodynamic indication (p=0.02), single ventricle (p=0.004), and diabetes mellitus (p=0.03) were predictors of prolonged time to chest closure. Amongst hospital survivors, there was no difference in late survival between patients undergoing DSC ≤4 days vs >4 days (p=0.48). Brief duration of DSC in ACHD patients is associated with low morbidity and mortality. Higher early mortality and complications were observed among patients who did not achieve chest closure within 4 days.