Flavonoids are natural compounds derived from different types of vegetables, fruits, and medicinal herbal plants. Hesperidin, a flavanone (a class of flavonoids) glycoside is found abundantly in citrus fruits such as oranges, lemons tangerines and limes and is known to possess significant benefits, such as anti-inflammatory, anti-stress, antioxidant, growth promoting, anticancer and immunological properties. Hesperidin enhances mucosal and humoral immunity by increasing intestinal intraepithelial lymphocyte numbers, lymphoid organs (thymus, spleen and bursa) indices, as well as improving anti-avian influenza and anti-Newcastle disease antibody titres in poultry. In addition, hesperidin is a strong chain-breaking antioxidant that provides potent cellular antioxidant defence against the damaging effects induced by peroxide hydrogen. As a natural antioxidant, hesperidin could help mitigate heat stress during summer by decreasing heterophil-to-lymphocyte ratios, and quenching reactive oxygen species generated by summer heat stress. The aim of this review was to elucidate the biological effects and health benefits of hesperidin as an alternative of synthetic immune boosters and growth promoters in poultry diets.