In view of the growing concern with about sub-therapeutic uses of AGP in animal; feed and greater appreciation of the role of the microbial ecology of the gastro-intestinal tract (GIT) in determining animal productivity, increasing numbers of probiotic products are being developed and used in animal nutrition and feeding Bacillus species are superior probiotic feed-additives for poultry and pigs due to their big genomes with relevant/desirable features. B. subtilis is certified as "generally recognized as safe" by Food and Drug Administration and features in the last of European Food Safety Authority, Qualified Presumption of Safety, hence suggesting as safe for human use. All of These beneficial attributes make B. subtilis the most attractive probiotic species for various clinical conditions. With this in view the present experiment was planned to study the effect of dietary supplementation of different strains of Bacillus subtilis as probiotic on growth performance, nutrient utilization and gut health in broiler chickens.