Background: Adults with congenital heart defects (CHDs) have an increased risk for cardiovascular complications, but few are in optimal cardiovascular health. Executive function deficits, which are elevated among CHD survivors, may contribute to engagement in behaviors that increase cardiovascular risk. Objective: The aim of this study was to identify the association between executive function and the health risk behaviors of tobacco use, saturated fat intake, and insufficient physical activity among young adults with CHDs. Methods: Young adults with CHDs completed the Behavior Rating Inventory of Executive Function-Adult Version, which yields composite and 9 individual domain scores (eg, inhibition, working memory). Participants also completed self-report measures of tobacco use, saturated fat intake, and physical activity. Linear and logistic regression models determined the association between executive function and risky health behaviors, adjusting for demographic factors, disease status, and emotional distress. Results: One in 10 young adults with CHDs reported clinically significant difficulties with global executive function. Difficulties with global executive function were associated with increased tobacco use ( P = .018) and greater saturated fat intake ( P = .015) but not insufficient physical activity ( P = .902). Difficulties with inhibition were specifically associated with increased tobacco use ( P = .003) and greater saturated fat intake ( P = .007), and problems with self-monitoring were associated with increased tobacco use ( P = .017). Conclusions: Executive function difficulties are associated with self-reported engagement in health risk behaviors among young adults with CHDs. Health behavior interventions for adult CHD survivors may require additional modifications that consider executive function problems, particularly difficulties with inhibition.