The present study investigated the effect of Dahi containing potential probiotic bacterial strains on macrophage functions in ageing mice. Probiotic Dahi was prepared by co-culturing Dahi bacteria (Lactococcus lactis ssp. cremoris and Lactococcus lactis ssp. lactis biovar diacetylactis) along with Lactobacillus acidophilus LaVK2 (La-Dahi) or combined L. acidophilus LaVK2 and Bifidobacterium bifidum BbVK3 (LaBb-Dahi) in buffalo milk. The effect of ageing on phagocytic function was evaluated on 4 mo, 12 mo and 16 mo old mice. The effect of probiotic Dahi was evaluated for macrophage functions in ageing mice (12 mo old) fed La-Dahi or LaBb-Dahi supplements for 4 months. The production of extracellular superoxide and H2O2 declined in peritoneal macrophages but enhanced in splenic macrophages, while intracellular superoxide declined in both peritoneal and splenic macrophages with ageing in mice. A decline in phagocytic activity of peritoneal macrophages was also observed in aged mice. Supplementation of diet with La-Dahi or LaBb-Dahi for 4 months improved production of reactive oxygen species and phagocytic and adherence indices of peritoneal macrophages in aged mice. These results suggest that oral administration of La-Dahi or LaBb-Dahi has potential to improve immune functions in ageing individuals.