Dysbiosis of the maternal gut microbiome during pregnancy is associated with adverse neurodevelopmental outcomes. We previously showed that maternal high-fat diet (MHFD) in mice induces gut dysbiosis, social dysfunction, and underlying synaptic plasticity deficits in male offspring (F). Here, we reason that, if HFD-mediated changes in maternal gut microbiota drive offspring social deficits, then MHFD-induced dysbiosis in F female MHFD offspring would likewise impair F social behavior. Metataxonomic sequencing reveals reduced microbial richness among female F MHFD offspring. Despite recovery of microbial richness among MHFD-descendant F mice, they display social dysfunction. Post-weaning Limosilactobacillus reuteri treatment increases the abundance of short-chain fatty acid-producing taxa and rescues MHFD-descendant F social deficits. L. reuteri exerts a sexually dimorphic impact on gut microbiota configuration, increasing discriminant taxa between female cohorts. Collectively, these results show multigenerational impacts of HFD-induced dysbiosis in the maternal lineage and highlight the potential of maternal microbiome-targeted interventions for neurodevelopmental disorders.