The aim of this study was to examine the effects of folic acid (FA) on the autistic phenotypes in BTBR T+ Itpr3tf/J (BTBR) mice and to investigate underlying mechanisms. Mice received FA (0.2 mg/kg/day) orally from postnatal days 14 to 35. Mice were then tested for stereotyped and repetitive behaviors, social interaction, and spatial learning and memory at the end of FA supplementation. Oxidative stress, neuroinflammatory responses and ferroptosis-related proteins in the brain were also evaluated. FA supplementation in BTBR mice reduced repetitive and stereotyped behavior, improved social communication, and enhanced memory and spatial learning. FA supplementation also reduced neuronal loss in hippocampal CA1 regions of the brain and decreased the levels of the proinflammatory cytokines such as interleukin-1β (IL-1β), Iba-1, IL-18, tumor necrosis factor-a, and IL-6 and glial fibrillary acidic protein in the hippocampus. FA supplementation changed the malondialdehyde and glutathione levels and superoxide dismutase (SOD) and glutathione peroxidase activities in the hippocampus. FA supplementation inhibited the elevation of the SOD1 and TFR protein levels and enhanced the relative expression levels of glutathione peroxidase 4 and ferroportin 1 in the hippocampus and increased the relative levels of phospho-Ca2+/calmodulin-dependent protein kinase II and phospho-cAMP-response element binding protein in the hippocampus. FA oral supplementation to BTBR mice rescued stereotyped and repetitive behaviors, social deficit, and spatial learning and memory impairments, likely by improving the oxidative-stress and inflammatory responses by altering the ferroptosis signaling pathways.