This book describes the process of immunomodulation and the plants which possess immunomodulation properties to boost the immune system. The immunomodulation process is highly relevant to address emerging as well as existing diseases in humans. A better immune system triggers the cellular responses for neutralizing and combating the onset of disease conditions. Chapters in the book discuss plants that have profound effects on the health and well-being of humans. They discuss the natural phytochemicals that have immense diversity and uniqueness of molecules. Molecules belonging to phenylpropanoids, terpenoids, steroids, alkaloids, and tannins etc possess a variety of pharmacological activities. The chapters describe how bioactive exert effects even when taken as part of the diet, supplement, and or as traditional herbal medicine. This book provides up-to-date scientific knowledge about the activities and mechanisms and leads in the area of medicinal plants and phytochemicals with immunomodulation properties.