Succinic semialdehyde dehydrogenase (SSADH) deficiency is an heritable disorder of GABA degradation characterized by ataxia, psychomotor retardation and seizures. To date, there is no effective treatment for SSADH deficiency. We tested the hypothesis that a ketogenic diet (KD) would improve outcome in an animal model of SSADH deficiency, the SSADH knockout mouse (Aldh5a1 −/− ). Using a 4:1 ratio of fat to combined carbohydrate and protein KD we set out to compare the general phenotype, in vivo and in vitro electrophysiology and [ 35 S]TBPS binding in both Aldh5a1 −/− mice and control (Aldh5a1 +/+ ) mice. We found that the KD prolonged the lifespan of mutant mice by >300% with normalization of ataxia, weight gain and EEG compared to mutants fed a control diet. Aldh5a1 −/− mice showed significantly reduced mIPSC frequency in CA1 hippocampal neurons as well as significantly decreased [ 35 S]TBPS binding in all brain areas examined. In KD fed mutants, mIPSC activity normalized and [ 35 S]TBPS binding was restored in the cortex and hippocampus. The KD appears to reverse toward normal the perturbations seen in Aldh5a1 −/− mice. Our data suggest that the KD may work in this model by restoring GABAergic inhibition. These data demonstrate a successful experimental treatment for murine SSADH deficiency using a KD, giving promise to the idea that the KD may be successful in the clinical treatment of SSADH deficiency.