The red yeast Phaffia rhodozyma is considered as a useful source of astaxanthin (ASX) which is a carotenoid pigment widely used in the feed industry. Poultry cannot synthesise carotenoids, so they must obtain these pigments from diet supplementation with sources such as red yeast, as a source of ASX. Astaxanthin has health benefits including the protection against oxidative damage in cells, enhancement of the immune response and protection against diseases by scavenging oxygen free radicals. It has activities approximately 10 times stronger than that of other carotenoids and 100 times greater than α-tocopherol against reactive oxygen species. In recent years, Phaffia rhodozyma has become an important microorganism for its use in both the pharmaceutical industries and food. Dietary Phaffia rhodozyma addition at the level of 10 and 20 mg/kg in broiler diets positively increased weight gain by 4.12 and 6.41% respectively. The inclusion of ASX rich red yeast (100 mg/kg) in broiler diets for 14 days improved T-cell proliferation and IgG production by 111.1 and 34.6% respectively. However, the optimum level or feeding duration of dietary ASX rich red yeast addition for enhancing poultry productive, physiological and immunological responses has not been determined.