Abstract: Background and Objective: Quercus dilatata is traditionally used for the treatment of various human diseases. The present study was conducted for the determination of in vivo anti-diabetic activity and diabetes complications preventive effect of the Quercus dilatata. Methodology: The methanol extract of Quercus dilatata (200 and 400 mg kg–1; orally) was administered in alloxan induced (150 mg kg–1; intraperitoneally) diabetic rats. Glibenclamide (10 mg kg–1 day–1 orally) was used as a standard drug. Diabetic rats boosted the levels of blood glucose, serum lipids (triglycerides, cholesterol, low density lipoprotein and serum high density lipoprotein levels), liver enzymes (serum alanine transaminase (ALT), alkaline phosphatase (ALP) and total bilirubin), serum urea, creatinine and total protein. Results: After 21 days of treatment, the plant extract at a dose of 200 and 400 mg kg–1 day–1 significantly reduced the elevated blood glucose level in diabetic rats by 114.975 and 111.520%, respectively. Extracts of Quercus dilatata (both doses) proved to have anti-diabetic activity by decreasing the elevated level of plasma blood glucose, with subsequent increase in body weight. Extracts of Quercus dilatata (both doses) also proved to have lipids, hepatic and renal protective activity by reducing the elevated level of enzymes and other biochemical markers. Extract at a dose of 200 mg kg–1 revealed highly significant (p<0.05)results as compared to 400 mg kg–1 dose. Conclusion: On the basis of the results it is concluded that Quercus dilatata extract can be used to treat diabetes, kidney and liver disorders and serum lipids related abnormality.