Nutraceuticals are natural bioactive products with food value and promising therapeutic properties in several diseases. Current cancer treatments, such as chemotherapy, radiotherapy and surgery, induce unintended side effects compromising also health and well-being of patients. Emerging studies suggest that some plant-based agents may impact cellular and molecular processes underlying tumor progression. However, some of these molecules might also play an antagonistic activity against classic therapeutic agents. The aim of this article is to review the current knowledge underpinning the use of nutraceuticals in cancer prevention and therapy.