Many studies have reported that adults with congenital heart disease suffer from hypertension and cardiovascular disease even at younger ages. Therefore, we analyzed early vascular aging, which is defined as pulse wave velocity values higher than the 95th percentile for age and sex, and clarified the relationship between early vascular aging and many parameters related to cardiovascular disorders in adults with congenital heart disease. We enrolled 72 adult patients with congenital heart disease and measured their brachial-ankle pulse wave velocity. Comparing the data between age- and sex-matched controls, patients with a pulse wave velocity higher than the 95th percentile for age and sex were defined as exhibiting early vascular aging. The parameters of patients with and without early vascular aging were compared. Early vascular aging was observed in 15.6% of the patients. Age, systolic blood pressure, diastolic blood pressure, pulse pressure, blood sugar, hemoglobin A1c, uric acid, low-density lipoprotein cholesterol, and triglyceride levels were positive determinants of early vascular aging. Logistic regression analysis proved that systolic blood pressure was a significant determinant of early vascular aging (odds ratio, 1.128, 95% confidence interval, 1.049-1.214; p = 0.001). The prevalence of early vascular aging is high in adult patients with congenital heart disease. Because early vascular aging can damage a patient's vulnerable heart, careful follow-up of blood pressure and pulse wave velocity is essential.