This study has investigated the antidiabetic potential of the extracts of Diodia sarmentosa (Rubiaceae) leaves on alloxan induced diabetic Wistar rats. The leaves are used to treat diabetes and various other disease conditions in traditional medicine. In this study, the leaves were air-dried and pulverized. A 1kg of the powdered leaves was extracted by maceration with n-hexane, chloroform and 70% methanol successively for three consecutive days, respectively. Phytochemical screening was conducted on the leaves using standard methods. Acute toxicity test was conducted on the rats by the Lorke’s method. Diabetes was induced by the intraperitoneal injection of 120mg/kg body weight of alloxan monohydrate to the rats. Results of the phytochemical screening showed the presence of cardiac glycosides, saponins, tannins, triterpenoids and carbohydrates. The acute toxicity test indicated the plant to be safe since no fatality was recorded on the rats even at the dose of 5000mg/kg body weight. The n-hexane extract produced a peak significant (p<0.05) reduction of 75.3% in the blood glucose levels of the rats at day 7, comparable to 82.38% reduction by the control drug, glibenclamide. The chloroform and aqueous methanol extracts did not exhibit significant reductions in blood glucose levels. This study suggests that the n-hexane extract of D. sarmentosa leaves possesses significant (p<0.05) antidiabetic activity. This tends to justify its use in ethnomedicine for the management of diabetes and its related conditions.