Pyridoxal-5'-phosphate oxidase (PNPO) deficiency is a rare autosomal recessive, vitamin-responsive metabolic disorder causing refractory neonatal seizures that respond to the administration of pyridoxal-5'-phosphate (PLP). There are currently few case studies that have documented the functional outcome in PNPO deficiency, which remains poor in the majority of cases. We present the case of a male infant born at 35 weeks gestation who promptly responded to oral administration of PLP, following resistance to common anticonvulsive therapy and to a pyridoxine trial. Neurological outcome at 21 months is favorable and illustrates the importance of standardized vitamin trials in the acute setting of "therapy-resistant" neonatal seizures. Early recognition of PNPO deficiency and appropriate intervention might be associated with a more favorable outcome than initially considered.