Survey has shown that the number of persons with diabetes mellitus (DM) would increase in the coming decade. Diabetes mellitus is primarily defined by the level of hyperglycemia which causes nephropathy. The present study investigated renal oxidative status of diabetic rats administered methanol fraction of ethanol extract of Dialium Guineense (MEDG) stem bark. Male Wistar rats (n = 25, mean weight = 215 ± 15 g) were randomly assigned to five groups (5 rats per group): normal control, diabetic control, metformin, and 200 mg/kg body weight (bwt) and 300 mg/kg bwt extract groups. Diabetes mellitus was induced via intraperitoneal injection of streptozotocin (STZ, 50 mg/kg bwt). The diabetic rats were then treated for 21 days with metformin (50 mg/kg bwt) or the extract at doses of 200 and 300 mg/kg bwt, respectively. The results showed that the activities of catalase, superoxide dismutase (SOD), glutathione peroxidase (GPX), and Glutathione Reductase (GR) as well as levels of reduced glutathione (GSH) and % GSH were significantly lower in diabetic control group than in the normal control group, but they were increased by MEDG treatment (p < 0.05). On the other hand, the levels of nitric oxide (NO) and malondialdehyde (MDA) elevated by STZ were markedly reduced after treatment with MEDG (p < 0.05). It can be concluded that MEDG stem bark possesses an ameliorative potential against STZ-induced oxidative stress in rats.