Polyphenols are the secondary metabolites synthesized by the plants as a part of defense machinery. Owing to their antioxidant, anti-inflammatory, anticancerous, antineoplastic, and immunomodulatory effects, natural polyphenols have been used for a long time to prevent and treat a variety of diseases. As a result, these phytochemicals may be able to act as therapeutic agents in treating cancer and cardiovascular and neurological disorders. The limited bioavailability of polyphenolic molecules is one issue with their utilization. For the purpose of increasing the bioavailability of these chemicals, many formulation forms have been developed, with nanonization standing out among them. The present review outlines the biological potential of nanoformulated plant polyphenolic compounds. It also summarizes the employability of various polyphenols as nanoformulations for cancer and neurological and cardiovascular disease treatment. Nanoencapsulated polyphenols, singular or in combinations, effective both in vitro and in vivo, need more investigation.