The prevalence of food allergies has increased in recent decades in industrialized developed countries. Defects are influenced by environmental factors in early life, including early colonizers of the human gut microbiota. Therapeutic solutions are limited, and the lack of efficient treatments has led to the search for new treatments, including biotherapies. Promising results from this search suggest that immunomodulatory probiotic bacteria, in particular, may yield new biotherapeutic or preventive strategies to address the increasing burden of food allergies. In this context, we investigated the potential impact of Propionibacterium freudenreichii CIRM-BIA129, a recognized immunomodulatory probiotic bacterium, on food allergy development in a murine model. Preventive effects of this probiotic were evaluated in the context of an induced wheat gliadin allergy. Following sensitization using gliadins, clinical and immunological parameters were monitored following an oral challenge with wheat gliadin. When consumed orally, P. freudenreichii CIRM-BIA129 prevented induced wheat gliadin allergy. Probiotic administration favored the differentiation of Treg cells at the expense of Th2 cells in mice. Notably, P. freudenreichii CIRM-BIA129 ΔslpB, which contains a mutation in the slpB gene encoding a key surface protein involved in adhesion and immunomodulation, failed to induce the same phenotype. Accordingly, the wild-type probiotic stimulated IL-10 production by human peripheral blood mononuclear cells, while the mutant did not. Altogether, these results indicate that the P. freudenreichii CIRM-BIA129 strain can mitigate the food allergic response through its immunomodulatory effects mediated by the surface layer protein SlpB. This finding provides new perspectives for biotherapies aimed at managing the increased prevalence of food allergy.