Nutraceutical, a term derived from ‘nutrition’ and ‘pharmaceutical’, refers to any product isolated from herbs, nutrients, specific diets, processed foods, and beverages used not only for nutritional but also for medicinal purposes. Nutraceuticals comprise many bioactive derivatives from edible sources such as anti-oxidants, phytochemicals, fatty acids, amino acids, prebiotics and probiotics. Many of them possess therapeutic properties that can affect the immune system. In this Special Issue, Al Ali et al.  offer a comprehensive review of nutraceuticals categorized based on their source, nature and application. The authors broadly classified the mode of actions of nutraceuticals into anti-cancer, anti-inflammatory, anti-oxidant, and anti-lipid activities. Nutraceuticals can augment the immune system to prevent cancer, neurological conditions, gastro enterological disorders, inflammatory diseases, and infections.