The anti-diabetic effects of Ribes khorasanicum as a traditional remedy were investigated in diabetic rats. Thirty-five male rats were divided into five groups: control, diabetic, diabetic treated with metformin (300 mg kg-1; D+Met), diabetic treated with 250 and 500 mg kg-1 of Ribes khorasanicum hydro-ethanolic extract (D+Rib250 and D+Rib500). After six weeks of treatment, sera of overnight fasted animals were collected and used for measurement of glucose, insulin, lipid profile, urea, creatinine, and hepatic enzymes levels. Moreover, liver and kidney of rats were removed and used for measurement of oxidative stress including malondialdehyde (MDA), thiol content, and the activity of catalase (CAT) and superoxide dismutase (SOD). Streptozotocin (STZ)-induced diabetes increased the levels of serum glucose, triglycerides (TG), total cholesterol (TC), and LDL-C, urea, creatinine, hepatic enzymes, and kidney and liver oxidative stress markers, while decreased insulin and HDL-C when compared to control group. In all treated groups serum levels of glucose, TC, LDL-C, TG, and urea were decreased, while liver SOD activity was increased compared to the diabetic group. The D+Rib500 group had lower Serum glutamic pyruvic transaminase (SGPT), creatinine, and kidney MDA levels, but higher insulin, HDL-C levels, liver CAT activity, and kidney thiol content, and CAT activity compared to diabetic group. In D+Met group, serum levels of serum glutamic-oxaloacetic transaminase (SGOT), creatinine, and MDA of liver and kidney were decreased, while liver SOD activity was increased compared to the diabetic group. Based on our findings, treatment with Ribes khorasanicum improved diabetic complications, while the effect of a higher dose of the extract was comparable to metformin’s.