The purpose of this study is to evaluate the effect of aqueous leaf extract of Moringa oleifera (orally administered) on blood glucose level, insulin and pancreatic beta-cells in alloxan-induced diabetic rats. Experimental method was adopted. Tanta University, Egypt between September 2013 and January, 2015. Sixty adult male albino rats of the Wistar strain weighing 99 +/- 1.03 g were used for this study. These were randomly assigned into 6 groups of 10 animals per group as; Group I: Normal control rats, Group II: Normal rats administered with low dose of moringa (200 mg/kg/d for 30 days), Group III: Normal rats given high dose of moringa (400 mg/kg/d for 30 days), Group IV: Diabetic rats, animals received only alloxan intraperitoneally and were not treated (served as Hyperglycemic group), Group V: Diabetic rats administered with low dose of moringa as in group II, Group VI: Diabetic rats administered with high dose of moringa as in Group III. At the end of the experiment, rats were sacrificed, and pancreatic specimens and blood samples were collected after 14 hours fast. Changes in the rats' blood levels of glucose and insulin were determined in all animal groups. Pancreatic histopathology and the IHC expression of insulin producing cells (beta-cells) were also examined. A significant increase in blood glucose and a significant decrease in insulin of diabetic rats were recorded when compared with the normal control group. Treated diabetic rats with high dose of Moringa oleifera extract recorded a significant decrease in blood glucose level and a significant increase in insulin. Low dose of moringa treatment to diabetic rats recorded slight decrease in plasma glucose and a slight increase in insulin. Histopathologically, diabetic rats treated with low dose of moringa showed no improvement of pancreatic islets and acinar cells, while the pancreatic tissues of diabetic rats treated with a high dose of moringa illustrated an obvious recovery of pancreatic islets and acinar cells to approximately normal status. By using IHC, the expression of insulin producing cells (beta-cells) that, were minimized in diabetic rats, restored in the rats group treated with high dose of moringa. Oral administration of Moringa oleifera extract at a high dose diabetic rats is considered as a strong anti-hyperglycemic, reduced the blood glucose and increased the insulin level as well as the histological improvement of the pancreatic tissues, minimized the degeneration of pancreatic beta-cells immunoreactivity and recovery the insulin producing cells (beta-cells).