Immune system in human body is an essential tool to fight against the harmful pathogens and protect the body from many diseases. The strengthening of the immune system builds a strong shield having balanced immune responses. This book is an attempt to explore our knowledge on traditional herbal drugs involved in strengthening immune homeostasis. The book has an exclusive chapter on the traditionally recommended and scientifically validated medicinal plants as immune stimulants and a chapter on basics of immunology. The ethnomedical considerations, pharmacognostic features, traditional recommendations as immune stimulants, mechanism of action and clinical investigations of some prominent plants are incorporated in the book, including Emblica officinalis, Tinospora cordifolia, Aloe vera, Allium sativum, Curcuma longa, Glycyrrhiza glabra, Boerhaavia diffusa.