Probiotic supplementation during critical windows of gestation might have a significant influence on the infant’s immune phenotype. Swiss albino mice (F0 generation) aged 31 days were supplemented orally with probiotic Lactobacillus rhamnosus GG (LGG); and the supplementation was continued throughout mating, gestation and lactation. The pups (F1 generation) born to them were separated post weaning and received either the same probiotic supplementation as their mothers or were denied supplementation postnatally. Neutrophil phagocytic ability, splenocyte proliferation, immunoglobulins and cytokines were determined in both F0 and F1 pups. In addition, antibody response against hepatitis-B surface antigen (HBsAg) was determined in F1 pups. Probiotic supplementation had no effect on the neutrophil phagocytic ability and splenocyte proliferation index. The serum immunoglobulin G (IgG) and secretory IgA (s-IgA) among the probiotic supplemented group of F0 generation were significantly (P<0.05) higher compared to the controls. Similarly, the mean concentration of interleukin (IL)-10, IL-17 and interferon gamma (IFN-γ) among F0 probiotic group were significantly higher (P<0.05) compared to the control. Prenatal and postnatal probiotic supplementation in F1 pups led to similar results as F0 dams. Prenatal probiotic supplementation in F1 pups led to significantly (P<0.05) higher serum IgG (55.15±1.35 ng/ml) and intestinal s-IgA (77.9 ± 2.86 ng/mg protein) concentration when compared to the control. Similarly, IFN-γ concentration increased (P<0.05) with prenatal probiotic supplementation compared to the control. However, IL-10 and IL-17 concentrations of prenatal probiotic supplemented F1 pups were comparable to the control. As for the antibody response to HBsAg, prenatal probiotic supplementation led to enhanced HBsAg antibody response (471.4±3.97 U/ml) compared to the control. LGG affected the immune regulation and immune responses favourably in mothers and offspring. In addition, some of the beneficial effects of prenatal LGG supplementation extended into postnatal life of the offspring, thus suggesting possible immunoprogramming effect of LGG.