Phytochemicals are endemic in the human diet from the ancient times to fight against diseases as most of the medicines were derived from plants. In the recent era, diet based therapy has been revitalized globally and people are adopting the approach of using natural materials as an intervention against various ailments. Black tea (Camellia sinensis) belonging to family Theaceae is one such example of functional drinks containing bioactive molecules holding cure against various diseases. Black tea occupied 80% of tea consumption of the world. It is fully fermented product and blessed with its distinguished bioactive molecules called theaflavin. Black tea inheriting with a complete nutrition and therapeutic package, which can be applied to reduce various modern life style disorders. This book has mainly highlighted the antioxidant potential, tea quality parameters and its application as a anti- diabetic drug.