In this study, supplementation with the probiotic Saccharomyces boulardii promoted a reduction in intensity of infection by Toxocara canis and modulates cytokines mRNA expression in experimentally infected mice. IL-12 gene transcription had 40-fold increase in S. boulardii supplemented uninfected mice and sevenfold increase in supplemented infected mice comparing with not supplemented group. Regarding IFNγ, similar results were observed, since probiotic supplementation induced approximately 43-fold increase, but only in uninfected mice (P < 0·05). T. canis infection upregulated IL-10 expression while S. boulardii downregulated it and no change was observed for IL-4. Thus, based in these findings; we suggest that one possible mechanism responsible for S. boulardii protection effect against T. canis infection is by the modulation of cytokines expression, especially IL-12.