Background: Doubly committed ventricular septal defect (dcVSD) is the least common type of VSD. Because published studies are rather scarce, this study aimed at evaluating the midterm outcome of dcVSDs. Methods: The records of all patients registered in the database of Paediatric and Congenital Cardiology, University Hospitals Leuven, with a dcVSD at 16 years of age were reviewed. Clinical, electrocardiographic and transthoracic echocardiographic changes from baseline, defined as of the age of 16 years, until the latest follow-up were compared. Results: Thirty-three patients (20 males, median age 26 years, interquartile range 12) were followed for a median time of 7.9 years (interquartile range 9.8, time range 2-25.9). No deaths occurred. In 15 patients (45%), the defect remained patent at baseline. During follow-up, two spontaneous closures (13%) occurred. Eighteen patients (55%) required closure before the age of 16 years. Five (28%) needed reoperation. In the dcVSD closure group, left ventricular ejection fraction decreased from 69 ± 12 to 61 ± 6% (p = 0.028). No significant changes in pulmonary arterial hypertension were noticed. Conclusions: Patients with persistently patent dcVSD remained nearly event free during follow-up. Event-free survival after dcVSD closure was markedly lower. These patients developed reduced left ventricular function and had a high risk of reintervention.