Type-2 diabetes (T2D) is a complex metabolic syndrome that is characterized by persistent hyperglycemia due to either lack of insulin secretion and/or insulin resistance. The prevalence of T2D along with its major risk factor, obesity, has been increasing with an epidemic proportion in recent years. To date, there is no drug of cure for diabetes and the existing therapeutic approaches have serious drawbacks including side effects and loss of efficacy during prolonged use. Dietary polyphenols are one group of natural products that have shown promise as potential antidiabetic agents. In this review, their molecular mechanisms of action including, antioxidant, anti-inflammatory, receptor agonist/antagonist effect and modulation of key signal transduction cascades, glucose transport, enzyme activity, receptor agonistic/antagonist effect, etc. in major insulin-sensitive cells are discussed.