Since the initial deployment of neonatal extracorporeal membrane oxygenation (ECMO) for respiratory failure, the use of ECMO in this population has diversified. We present a term female infant with carbamoyl phosphate synthetase 1 and partial N-acetylglutamate synthase deficiencies who developed severe hyperammonemia refractory to medical management requiring venoarterial ECMO-driven continuous veno-venous hemodiafiltration for ammonia detoxification. This case report illustrates a subpopulation where neonatal ECMO may improve survival and neurodevelopmental outcomes. To our knowledge, this is the first reported case of a urea cycle defect arising from two proximal enzyme deficiencies. Also, this is one of the few reported patients with UCD associated with peak ammonia levels >2,000 μmol/L who survived to hospital discharge after the successful use of ECMO for ammonia reduction. This case will add to the existing scant literature supporting the use of ECMO as a platform for rapid removal of serum ammonia.