Little is known about outcomes following heart failure (HF) hospitalization among adults with congenital heart disease (CHD) in the United States. We aim to compare the outcomes of HF versus non-HF hospitalizations in adults with CHD. Using a national deidentified administrative claims data set, patients with adult congenital heart disease (ACHD) hospitalized with and without HF (ACHDHF+, ACHDHF-) were characterized to determine the predictors of 90-day and 1-year mortality and quantify the risk of mortality, major adverse cardiac and cerebrovascular events, and health resource use. Cox proportional hazard regression was used to compare ACHDHF+ versus ACHDHF- for risk of events and health resource use. Of 26 454 unique ACHD admissions between January 1, 2010 and December 31, 2020, 5826 (22%) were ACHDHF+ and 20 628 (78%) were ACHDHF-. The ACHD HF+ hospitalizations increased from 6.6% to 14.0% (P<0.0001). Over a mean follow-up period of 2.23 ± 2.19 years, patients with ACHDHF+ had a higher risk of mortality (hazard ratio [HR], 1.86 [95% CI, 1.67-2.07], P<0.001), major adverse cardiac and cerebrovascular events (HR, 1.73 [95% CI, 1.63-1.83], P<0.001) and health resource use including rehospitalization (HR, 1.09 [95% CI, 1.05-1.14], P<0.001) and increased postacute care service use (HR, 1.56 [95% CI, 1.32-1.85], P<0.001). Cardiology clinic visits within 30 days of hospital admission were associated with lower 90-day and 1-year all-cause mortality (odds ratio [OR], 0.62 [95% CI, 0.49-0.78], P<0.001; OR, 0.69 [95% CI, 0.58-0.83], P<0.001, respectively). HF hospitalization is associated with increased risk of mortality and morbidity with high health resource use in patients with ACHD. Recent cardiology clinic attendance appears to mitigate these risks.