BackgroundMetabolic syndrome increases risk for atherosclerotic coronary artery disease, and its prevalence increases with increasing age and body mass index. Adults with congenital heart disease (ACHD) are now living longer and accruing coronary artery disease risk factors. However, the prevalence of metabolic syndrome in ACHD patients is unknown.Methods and ResultsWe conducted a retrospective cohort study of ACHD patients at our center to quantify the prevalence of metabolic syndrome in an ACHD population. Using case‐control matching, we constructed a comparable control group from a population‐based sample of 150 104 adults. International Diabetes Federation criteria were used to define metabolic syndrome. We used logistic regression to compare the risk of metabolic syndrome across the resulting cohorts, which were composed of 448 ACHD patients and 448 controls matched by age and sex. Mean age of both groups was 32.4±11.3 years, and 51.3% were female. Obesity was present in 16.1% of the ACHD patients and 16.7% of the controls. Metabolic syndrome was more common in ACHD patients than in controls (15.0% versus 7.4%; odds ratio 1.82, 95% CI 1.25–2.65).ConclusionsOur data suggest that metabolic syndrome is more common among adults with congenital heart disease than in the general population. Thus, patients with congenital heart disease should be screened for metabolic syndrome and risk factors mitigated where possible to prevent atherosclerotic coronary artery disease. Preventive cardiology should be included during routine ACHD care.