In conjunction with histone modifications, DNA methylation plays critical roles in gene silencing through chromatin remodeling. Changes in DNA methylation perturb neuronal function, and mutations in a methyl-CpG–binding protein, MeCP2, are associated with Rett syndrome. We report that increased synthesis of brain-derived neurotrophic factor (BDNF) in neurons after depolarization correlates with a decrease in CpG methylation within the regulatory region of the Bdnf gene. Moreover, increased Bdnf transcription involves dissociation of the MeCP2–histone deacetylase–mSin3A repression complex from its promoter. Our findings suggest that DNA methylation–related chromatin remodeling is important for activity-dependent gene regulation that may be critical for neural plasticity.