Nutrition is a cornerstone of overall health, safeguarding the body against diseases. During gestation, the quality of nutrition directly impacts a child's health. A mother's immune system and diet shape the child's immune system. As one ages, the immune system matures, demanding increased energy and supplements to match evolving physical attributes. Physical activity and the immune system are intertwined, with nutritional sources like carbohydrates and fatty acids along with supplementation with vitamins, minerals, and polyphenols playing pivotal roles in immune development. Consumption of probiotics and prebiotics further enhance immunity. Various cells of immune system and proteins produced by them help safeguarding against infections. Immune system is dependent on nutritional factors for proper function, and deficiencies lead to immune dysfunction. Balancing nutrition, the immune system, and body homeostasis is vital. This chapter provides an insightful overview of how various nutritional factors influence the immune system, emphasizing the need for a balanced approach to maintain a healthy immune system.