Recurrent aortic arch obstruction (RAAO) remains a major cause of morbidity following surgical neonatal repair of coarctation of the aorta (CoA). Elucidating predictors of RAAO can identify high-risk patients and guide postoperative management. The Coarctation index (CoA-I), defined as the ratio of the diameter of the narrowest aortic arch segment to the diameter of the descending aorta, has been used to help diagnose RAAO in neonates following the Norwood Procedure. We sought to assess the predictive value of the CoA-I on RAAO after CoA repair in infants with biventricular circulation. Clinical, surgical, and echocardiographic data of infants with biventricular circulation following neonatal CoA repair between 2010 and 2014 were evaluated. RAAO was defined using a composite quantitative outcome variable: a blood pressure gradient >20, a peak aortic arch velocity >3.5 m/s by echocardiogram, or a catheter-measured peak-to-peak gradient >20 within 2 years of surgery. Univariate and multivariate logistic regression analyses were used. Of the 68 subjects included in the analysis, 15 (22%) met criteria for RAAO. In the multivariate model, only CoA-I (OR 35.89, 95% CI 6.08–211.7, p < 0.0001) and use of patch material (OR 9.26, 95% CI 1.57–54.66, p = 0.014) were associated with increased risk of RAAO. The odds of developing RAAO was higher in patients with a CoA-I less than 0.7 (OR 33.8, 95% CI 5.7–199.5, p < 0.001). Postoperative CoA-I may be used to predict RAAO in patients with biventricular circulation after repair of CoA. Patients with a CoA-I less than 0.7 or patch aortoplasty warrant close follow-up.