Background & Aims: Considering increasing incidence of cardiovascular disorders in diabetes mellitus and some evidence on antioxidant and antidiabetic potentials of naringenin, this study was conducted to evaluate the beneficial effects of 6-week administration of naringenin on contractile reactivity of isolated thoracic aorta in diabetic rats. Methods: Male Wistar rats were divided into control, naringenin-treated control, diabetic and glibenclamide-treated, and naringenin-treated diabetic groups. For induction of diabetes, streptozotcin (STZ) was administered (60 mg/Kg). Naringenin (10 mg/kg) was administered i.p. one week after diabetes induction in every other day intervals for 6 weeks. Serum glucose level was measured before naringeninadministration and at 6th week. Finally, contractile reactivity of thoracic aortic rings to KCl and phenylephrine (PE) was cumulatively determined. Results: Serum glucose level at week 6 showed a significant decrease in naringenin-treated diabetic group compared to diabetics (P<0.01). In addition, naringenin-treated diabetic group showed a significantly lower contraction to PE (P<0.05) as compared to diabetic group and such significant reduction was also observed for KCl (P<0.05). Meanwhile, there was also a significant difference between control and naringenin-treated control groups regarding their contractile reactivity to PE (P<0.05). Conclusion: Subchronic administration of naringenin for 6 weeks could exert an anti-hyperglycemic effect and lowers contractile responsiveness of thoracic aorta rings to KCl and phenylephrine.