Autism spectrum disorders are associated with an imbalance of immune and neurological disorders, starting after the age of two. The study is devoted to studying the role of specialized strains of bacteria Lactobacillus reuteri, which mediate the synthesis of oxytocin in humans and influence inflammation indicators. Bacteria of this strain were part of the biologically active additive “Panbiolact Mental”, developed and presented by NPO ArtLife (Tomsk). The purpose of the work was to assess the effect of specialized strains of bacteria Lactobacillus reuteri on changes in the composition of the intestinal microbiota, oxytocin levels, and immune parameters of children with ASD. The study included 43 children with autism spectrum disorders who took Panbiolact Mental for 90 days. The study materials included venous blood samples and fecal samples. The concentrations of cytokines (IL-4, IL-10, TNF, IFN), immunoglobulins (IgE, IgG, IgA, IgM) and the neuropeptide oxytocin were determined in the blood serum. Fecal samples were used to assess the qualitative and quantitative composition of the colon microbiota. Clinical symptoms of the disease associated with quality of life were assessed using the standard ATEC test scale (Autism Treatment Evaluation Checklist), expressed in scores corresponding to the severity of clinical and neurological parameters of the disease. In children with autism spectrum disorders, after 90 days of regular use of Panbiolact Mental, the number of bacteria of the genera Acinetobacter decreased, the number of Bacteroides species pluralis, Akkermansia muciniphila, Eubacterium rectale, Prevotella species pluralis and Methanobrevibacter smithii increased. Increases in the concentration of oxytocin, the protolerogenic coefficient IL-10/TNFα, immunoglobulins M and G, and a decrease in the concentrations of TNFα and IL-10 were recorded. The results of the study support the hypothesis of a significant role of gut microbiota diversity in the neuro-immune pathogenesis of autism spectrum disorders. “Panbiolact Mental” is presented as a potentially effective remedy for an integrated approach to the correction of ASD in children. These data may form the basis for further research in the field of probiotic therapy, as well as for the development of new strategies based on modulation of the intestinal microbiota.