Diabetes are a serious metabolic diseases characterized by abnormally increased plasma glucose levels. Botanical food products have been used for combating human diseases for thousands of years, since they exhibit a wide range of biological properties that can be exploited for medical application. Phytochemicals from foods, including flavonoids, monoterpenes, terpenoids, stilbenes, lignans, coumarins, alkaloids, and others, have been proposed as effective supplements for diabetes management and prevention of its long-term complications in vitro and in vivo. The mechanism of antidiabetic activity of dietary phytochemicals could be summarized as: stimulation of insulin secretion from pancreatic beta-cell, reduction of insulin resistance and increasing of insulin sensitivity, stimulation of glycogenesis and hepatic glycolysis, activation of PPAR gamma, anti-inflammatory and antioxidant effects, inhibition of alpha-amylase, beta-galactocidase and alpha-glucocidase, and inhibition intestinal absorption of glucose. Therefore the anti-diabetic effects and their mechanism of action of phytochemicals from botanical foods used traditionally in the treatment of diabetes mellitus are critically reviewed.