Background: Studies on long-term outcomes of the arterial switch operation (ASO) for transposition of the great arteries (TGA) are uncommon. Thus, we sought to determine the long-term outcomes for patients after ASO performed at a single institution over a 25-year period. Methods: From 1983 to 2009, 618 patients underwent the ASO for TGA and were reviewed retrospectively. Results: Overall early mortality was 2.8%. Risk factors for early death on multivariate analysis were resection of left ventricular outflow tract obstruction at time of ASO (p = 0.001), weight less than 2.5 kg at time of ASO (p < 0.001), associated aortic arch obstruction (p = 0.043), and the need for postoperative extracorporeal membrane oxygenation (p < 0.001). Mean follow-up time was 10.6 years (range 2 months to 26.1 years). Late mortality was 0.9%. Reintervention was significantly higher (p < 0.001) in patients with ventricular septal defect or arch obstruction versus those without them (25.2% and 23.4% vs 5.9% at 15- year follow-up). Risk factors for late reintervention were left ventricular outflow tract obstruction at time of ASO (p < 0.001) and a greater circulatory arrest time (p < 0.001). Freedom from at least moderate neoaortic valve regurgitation for the entire cohort was 98.7% (95% confidence interval 96.8 to 99.5%) at 20 years. Mild neoaortic regurgitation was seen in 25.6% of patients at mean follow-up. All patients were free of arrhythmia and heart failure symptoms at last follow-up. Conclusions: The ASO can be performed with good long-term results. Patients with associated ventricular septal defect and aortic arch obstruction warrant close follow-up.