Cocoa is derived from the seeds of Theobroma cacao L., an evergreen tree typical of tropical regions. It contains numerous phytochemicals, with polyphenols representing the largest groups of compounds inside the seed, and has been implicated in numerous biological properties, such as antioxidant, antiproliferative, antiapoptotic, anti-inflammatory, anti-cancer. Moreover, cocoa has been investigated in different health conditions, including heart diseases, dyspepsia, nervous system diseases, circulation problems, and many others. Given its high consumption in many countries all over the world, it is important to know and understand its effects on human health. In addition, the cocoa bean shell, a by-product of the process of cocoa preparation, has been gaining remarkable interest due to its high content of phytochemicals. This review summarizes the available literature and works on the health benefits of cocoa and cocoa bean shells. Moreover, the current review focuses on studies investigating their possible therapeutic roles in cancer and the underlining potential mechanisms of action.