Classically, methylmalonic acidemia (MMA) is characterized on imaging by abnormalities in the basal ganglia, specifically the globus pallidi, as well as occasional signs of delayed maturation. We report a case of MMA in which abnormal signal and diffusion restriction occurred in the subcortical white matter, sparing the classically involved globus pallidi, a situation that has not been previously reported in the literature. This report demonstrates that diffusion abnormality can be seen in the white matter in MMA, in the absence of basal ganglia involvement, and that MMA may be considered when the diagnosis of metabolic acidemias is raised.