The incorporation of medicinal herbs into animal nutrition is gaining momentum as a natural alternative to synthetic antibiotics and chemical growth promoters. This chapter explores the functional properties of key herbal bioactive compounds—such as flavonoids, alkaloids, essential oils, and saponins—and their roles in enhancing animal health and productivity. These phytogenic additives improve gut integrity, boost immune function, and strengthen the antioxidant defense system. In livestock and poultry, herbal supplementation has been shown to improve feed intake, growth performance, and resistance to diseases. However, the effectiveness of these herbs is influenced by factors such as plant species, dosage, and method of preparation. Further research is essential to optimize formulations and ensure their safety across different animal species.