Probiotics and prebiotics boost poultry gut health and immunity. This chapter discusses current research and practical applications of these microbial-based supplements for chicken production. The chicken industry has struggled recently with gastrointestinal disorders, poor meal absorption, and viral infections. Probiotics and prebiotics, non-digestible food additives that boost gut microorganisms, may help. This chapter book explains probiotic and prebiotic interactions with avian gut flora. Probiotics and prebiotics impact poultry intestine bacteria balance, architecture, nutrient digestion, and immune control. The chapter also discusses issues in using probiotics and prebiotics. The chapter aims to provide a comprehensive reference for researchers, poultry nutritionists, veterinarians, and industry professionals interested in the potential benefits and practical applications of probiotics and prebiotics in poultry.