A priority in the prevention and correction of immune disorders in athletes is the use of products with high nutrient density, fortified with various nutrients or bioactive compounds, as well as probiotic microorganisms. Probiotics help to maintain the gut microbiota, which is actively involved in the absorption of substances and energy and increases the host immune resistance. Dietary fiber, resistant to digestion in the small intestine, is fully or partially fermented in the large intestine and acts as an essential substrate for the growth and regulation of metabolic activity of normal flora, improves peristalsis and digestion. The purpose of the study was to evaluate the impact of a multi-strain probiotic in combination with dietary fiber on the immune status of basketball athletes during the training period. Material and methods. The study was conducted with the participation of 30 male basketball athletes aged 18 to 24 years. The athletes were randomly divided into 2 groups of 15 people. Athletes in the main group received 1 capsule of multi-strain probiotic (≥1.25×1010 CFU of 10 probiotic strains of bifidobacteria and lactobacilli) and 40 g of corn bran (as a source of dietary fiber) for 23 days. Athletes in the control group received 1 placebo capsule containing maltodextrin and breadcrumbs (40 g/day). Subpopulations of peripheral blood lymphocytes were studied by flow cytometry: T lymphocytes, T helper cells, T cytotoxic lymphocytes, NK cells, NKT cells, B lymphocytes, as well as lymphocytes carrying activation markers and apoptosis marker antigen. The content of cytokines in blood serum [FGF, Eotaxin, G-CSF, GM-CSF, IFN-γ, IL-1ra, IL-1β, IL-2, IL-4, IL-5, IL-6, IL-7, IL-8, IL-9, IL-10, IL-12(p70), IL-13, IL-15, IL-17A, MCP-1, MIP-1α, MIP-1β, PDGF-BB, RANTES, TNF-α, VEGF] was determined using a multiplex immunoassay. Results. Calculation of the absolute number of lymphocytes revealed a tendency (0.05<p<0.10) to a decrease in T helper cells by the end of the observation period in athletes of the main group (497.60±27.67 vs 632.67±65.20 cells/μL), as well as a decrease (p<0.05) in the expression of the CD95/Fas apoptotic marker on peripheral blood lymphocytes of athletes of the main group compared to the beginning of the study (41.53±5.78 vs 69.53±11.79 cells/μL). At the end of the study, a significant increase in IL-9 level was found in the control group [(Me; min-max) = (0.33; 0.21-0.48) vs (0.26; 0.09-0.38) pg/ml; p<0.05; in comparison with the initial indicator]; as well as the tendency (0.05<p<0.10) towards an increase in the levels of IL-15, IL-1ra and RANTES was revealed. In the main group, at the end of the study, the level of G-CSF significantly decreased [(0.36; 0.03-0.95) vs (0.53; 0.14-1.36) pg/ml, p<0.05]. At the end of the observation period, blood serum levels of FGF, G-CSF, IL-13, IL-2 and RANTES in the athletes of the control group exceeded these indicators in the athletes of the main group whereas no significant differences in the studied cytokines were detected between the control and the main groups at the beginning of the study. Conclusion. The results of observation of basketball athletes who consumed a multi-strain probiotic in combination with corn bran (sources of arabinoxylans) in addition to the main diet for 23 days indicate a decrease in the inflammatory process activity and peripheral blood lymphocyte apoptosis, which confirms the effectiveness of probiotics and dietary fiber in sports nutrition.