Significant evidence suggests that polyphenol-rich diets have the ability to protect against diabetes. Since several previous reviews focused on the nutrition and health effects including type 2 diabetes of polyphenols in 2007-2008, a number of related original publications have been pulished in this field. This review summarizes important advances related to influence of dietary polyphenols and polyphenol-rich diets on preventing and managing type 2 diabetes, as well as diabetes-mediated changes in bioactivities of dietary polyphenols. It appears that anthocyanins or anthocyanin-rich food intake is related to the risk of type 2 diabetes, but there is no association for other polyphenol subclasses. It is discussed that procyanidins are more active when administered individually than when mixed with food. The benefits of dietary polyphenols for type 2 diabetes can be summarized as: protection of pancreatic β-cells against glucose toxicity, anti-inflammatory and antioxidant effects, inhibition of α-amylases or α- glucosidases and thus decrease of starch digestion, and inhibition of advanced glycation end products formation. Moreover, type 2 diabetes also significantly influences the benefits of dietary polyphenols, although there are very limited studies have been conducted so far. How type 2 diabetes impacts the pharmacology of dietary polyphenols is not well understood. Comprehension of type 2 diabetes-mediated changes in pharmacokinetics and bioactivity of dietary polyphenols might lead to improve the benefits of these phytochemicals and subsequent clinical outcomes for type 2 diabetics.