Mothers experiencing depressive symptoms or gestational stress are at risk of developing maternal distress, which, in its most severe form, can progress to postpartum depression, profoundly affecting maternal well-being and infant care. Using a late-gestation restraint stress model, we investigated whether postpartum treatment of lactating dams with probiotic Limosilactobacillus reuteri (L. reuteri) could reverse stress-induced disruptions in maternal behavior and neurobiology. L. reuteri effectively improved maternal care, and restored reactivity to pup separation in stressed dams. Postpartum L. reuteri also corrected corticosterone-oxytocin imbalances in plasma, normalized hypothalamic oxytocin levels, the unglycosylated and glycosylated oxytocin receptor isoforms and it regulated the ratio of precursor to mature brain-derived neurotrophic factor (BDNF). Additionally, L. reuteri restored gut microbiota balance, increasing Lactobacillus spp. while reducing pathogenic strains in fecal pellets of stressed dams during lactation and post-weaning, correlating with both maternal oxytocin and corticosterone plasma levels. This study is the first to demonstrate the therapeutic efficacy of a probiotic and its molecular support in counteracting the adverse effects of gestational stress on maternal care through brain-gut axis mechanisms. These findings support probiotic-based interventions as safe, complementary preventive strategy for improving maternal health in conditions involving impaired maternal care and microbiota dysbiosis.