Aims The present work was aimed to find novel probiotics to enhance the mucosal barrier function of humans. The effectiveness was evaluated in vitro and in vivo. Methods and Results Stimulation of IgA production in mucosal surfaces is one of the most beneficial traits of lactic acid bacteria (LAB) for enhancing the barrier. Therefore, 173 LAB strains were evaluated for the ability to induce IgA production using murine Peyer's patch cells. Strain NTM048 isolated from green peas showed the highest activity and was identified as Leuconostoc mesenteroides subsp. mesenteroides. This strain was found to tolerate gastrointestinal digestion and produce large amounts of exopolysaccharides, which possess IgA-inducing activity. Dietary supplementation with NTM048 induced a significant increase in the faecal IgA content and plasma IgA levels of BALB/cA mice. A gene expression analysis of Peyer's patch cells revealed that the transforming growth factor-beta and activation-induced cytidine deaminase genes were upregulated by NTM048 intake. Conclusions Strain NTM048 stimulates Peyer's patch cells to induce intestinal and systemic immune response, revealing the potential of NTM048 as a probiotic for enhancing the mucosal barrier function. Significance and Impact of the Study This report demonstrates a food-applicable Leuconostoc mesenteroides strain secreting exopolysaccharide that shows high IgA-inducing ability.