Nutrition has long been recognised to cause metabolic changes in muscles, such as tissue remodelling, increased protein turnover, and muscular atrophy. From a production standpoint, these modifications have an impact on production efficiency and meat quality. As a result, they are extremely valuable economically. Nutritional constraints related to specific dietary components and management measures can be difficult to determine quickly. Nutritional genomics describes the nutrient–gene interactions, as it includes two areas, nutrigenomics and nutrigenetics. The term ‘nutrigenomics’ refers to the study of the effects of nutrients/bioactive foods on an individual’s gene expression. In the other hand, nutrigenetics describes that the genetic profile has an impact on the response of body to bioactive food components by influencing their absorption, metabolism, and site of action. The inclusion of nutrients and nutraceuticals in poultry production can enhance gene expression of different genes related to health, metabolism, growth, immunity, and antioxidants. This review aims to shed the light on the definition of nutrigenomics and nutrigenetics in poultry nutrition.