A number of experimental and clinical findings have consistently demonstrated the protective effects of Pycnogenol (PYC) in the management of diabetes. However, the protective mechanism by which PYC provides protection in a model type I diabetes has not been studied. This study examines the beneficial effect of PYC on hyperglycemia, inflammatory markers, and oxidative damage in diabetic rats. We also evaluated the possible mechanism of action of PYC which might be that it stimulates beta islet expression, which has been implicated in the process of insulin secretion and diabetes management. Diabetes was induced in rats by an intraperitoneal injection of streptozotocin (STZ; 60 mg/kg body weight) followed by free access to 5 % glucose for the next 24 h. Four days after STZ injection, rats were supplemented with PYC (10 mg/kg body weight) for 4 weeks. At the end of the experiment, blood was drawn, and rats were then sacrificed, and their livers and pancreases were dissected for biochemical and histological assays. The level of fasting blood glucose and glycosylated hemoglobin significantly increased but amylase, insulin, and hepatic glycogen level decreased in the STZ group. PYC significantly augmented these effects in STZ + PYC group. The STZ group showed elevated level of nitric oxide, tumor necrosis factor-α, and interleukin-1beta in serum which were decreased by PYC treatment. Moreover, PYC significantly ameliorated increased thiobarbituric reactive substances, protein carbonyl, and decreased levels of glutathione, glutathione-s-transferase, and catalase activity in the liver and pancreas of the STZ rats. Histopathological and immunohistochemical examination also revealed a remarkable protective effect of PYC. The study suggests that PYC is effective in reducing diabetic-related complications in a type I model of diabetes and might be beneficial for the treatment of diabetic patients.