Methylmalonic acidemia (MMA) is a multifactorial autosomal recessive inborn error of organic acid metabolism, often presenting with neurologic findings. We report the imaging findings in a case of a child with classic neurological and laboratory findings for MMA. Imaging studies demonstrated abnormalities within the basal ganglia, particularly the globi pallidi (GP). Diffusion-weighted abnormalities seen in patients with MMA during an acute episode of metabolic acidosis and at follow-up are discussed. The authors are aware of only one prior report of serial examinations demonstrating resolution of restricted diffusion in the GP. The biochemical and pathophysiologic basis of the imaging findings of MMA are explained.