Objective: The use of angiotensin receptor blockers (ARB) has been related to delayed onset of type 2 diabetes mellitus (T2DM) in high-risk population, and valsartan treatment was reported to increase insulin secretion and sensitivity in participants with pre-diabetes. However, such phenomena have not been established in patients with T2DM. Therefore, we studied effects of ARB on glucose metabolism in T2DM. Methods: This is a randomized, open-labeled, active comparator-controlled and crossover study. Adults with T2DM having HbA1c < 8.5% and with hypertension were enrolled. Insulin users were excluded. After obtaining informed consent, amlodipine was administrated for two weeks targeting blood pressure below 140/90 mm Hg. Then, the patients were assigned to take either fimasartan (60~120 mg daily) or amlodipine (5~10 mg daily) in the order of enrollment for 16 weeks. Thereafter they switched to the other one for 16 weeks. Before and after each treatment, clinical and laboratory examinations were performed. Area under the concentration curves (AUC) during a 2-hr 75 g oral glucose tolerance test was calculated. The results were analyzed using paired t-test and Wilcoxon-matched pairs singed rank sum test. Results: Forty one patients were enrolled with mean age of 65.9 years, BMI 26.3 kg/m2, duration of diabetes 14.2 years, and blood pressure 129/80 mm Hg on amlodipine. Among them, 23 participants completed the study and preliminary analyses were performed with them. Blood pressure, HbA1c, and glucose tolerance were comparable between the treatments. Insulin secretory indices were significantly higher by fimasartan compared to amlodipine: AUCinsulin/AUCglucose (18.8 ± 15.5 vs 15.1 ± 11.2), Δinsulin60/Δglucose60 (30.3 ± 33.6 vs 22.6 ± 23.7) and HOMA-β (64.6 ± 42.6 vs 49.7 ± 25.3) (P < 0.05, respectively). However, Δinsulin30/Δglucose30 and HOMA-IR were not different between the agents. Conclusion: According to our preliminary results, fimasartan treatment increased 2nd phase insulin secretion in T2DM patients compared to amlodipine, suggesting ARB could be more favorable choice for hypertensive patients with T2DM.