In the present study, we evaluated the relative abundance of AT2R protein in various tissues of adult rats. We found that pancreatic islets expressed the highest AT2R protein as compared to all other tissues. Accordingly, we then determined the functional significance of AT2R in the endocrine pancreas in vivo and in vitro experiments by using Angiotensin II alone, Losartan (Los; AT1R antagonist), Compound 21 (C21; AT2R agonist), and PD123319 (PD; AT2R antagonist). Experiments carried out in rats indicated that, (1) Ang II treatment significantly increased plasma insulin concentration (1.51 ± 0.20 vs 0.82 ± 0.14 ng/ml, n = 7, P < 0.05) in the fed state. This insulinotropic effect was further augmented by combined treatment with Ang II plus Los (2.31 ± 0.25 ng/ml, n = 7, p < 0.01). C21 also elevated insulin levels (2.13 ± 0.20 ng/ml, n = 7, P < 0.01), which was completely abolished by PD. (2) Ang II impaired glucose tolerance, whereas Ang II plus Los or C21 improved this function. (3) All treated rats displayed an enhanced insulin secretory response to a glucose challenge. (4) All treated rats displayed up-regulated proinsulin 2 mRNA and insulin protein expression in the pancreas. In in vitro experiments using INS-1E cells and isolated rat islets, we found that AT2R activation significantly improved insulin biosynthesis and secretion. These results suggest that the AT2R functions as an insulinotropic mediator. AT2R and its downstream signaling pathways may be potential therapeutic targets for diabetes.