Caffeic acid is a phenolic acid naturally occurring in many plant foods such as carrots, cabbage, tomatoes, and several berries. It is also present in multiple beverages such as coffee, fruit juices and wine. Moreover, caffeic acid is one of the major active components in many traditional Chinese medicines. As a natural product, it possesses several biological and physiological activities. These activities include antioxidant, anti-mutagenic, anti-tumor and anti-obesity effects. For these reasons, caffeic acid is also being developed into drug for sale, for instance, for its use in the development of asthmatic and allergenic drugs. Although caffeic acid, together with other polyphenols, are not essential nutrients, they are secondary metabolites synthesised by plants with bioactive properties, also known as phytochemicals, which may have an important effect on human health. This book reviews sources, potential uses and health benefits of caffeic acid.