Succinic semialdehyde dehydrogenase deficiency (SSADHD), a disorder of γ-aminobutyric acid (GABA) metabolism, manifests typically as a nonprogressive neurodevelopmental disorder with cognitive deficiency, neuropsychiatric morbidity and epilepsy. Therapy targets symptomatic seizures and neurobehavioral disturbances. We report an adolescent female with SSADHD whose unresponsiveness to a broad spectrum of antiepileptics was circumvented with magnesium valproate (MgVPA). Epilepsy remains well controlled in our patient, with concomitant improvements in behavioral symptoms and an absence of adverse symptoms. MgVPA intervention may have utility in SSADHD.