Polyphenols refers to a broad family of naturally occurring organic compounds that are distinguished by the presence of several phenol units. They are abundantly found in plants and are structurally diverse. Polyphenols can be found in a variety of plant-based foods and beverages including nuts, fruits, wine, soy, vegetables, tea and spices. A diet high in vegetables and fruits may reduce the chance of developing certain types of cancer. Natural polyphenols are known to decrease the risk of cancer through their anti-cancer mechanisms such as anti-inflammation, modulation of cell cycle signaling, removal of anticancer agents, and activity of antioxidant enzymes. They also regulate numerous molecular events implicated in carcinogenesis such as apoptosis and arrest of the cell cycle. This book aims to understand the therapeutic effects of polyphenols in treating cancer. From theories to research to practical applications, case studies related to all contemporary topics of relevance to this area of study have been included herein. The book will help new researchers by foregrounding their knowledge on this topic.