We report a 51-year-old woman with vitamin B12 deficiency who presented with slight megaloblastic anemia and severe neurologic deficits associated with multiple focal and confluent T2-weighted white matter hyperintensities on brain MRI. Forty-four months after initiation of hydroxocobalamin therapy, there was clinical improvement and striking reduction in the MRI abnormalities. B12 deficiency should be considered in the differential diagnosis of neurologic disorders associated with multiple areas of white matter hyperintensities on T2-weighted brain MRI.