Study was conducted to evaluate the effects of Seabuckthorn leaf extract (SLE) supplementation on biochemical parameters in streptozotocin (STZ) induced diabetes mellitus in Wistar rats. Thirty-two adult male Wistar rats were divided into four groups namely CON (negative control), SCO (Seabuckthorn control), DCO (Diabetic control), and DSL (Diabetic seabuckthorn treatment group). Diabetes mellitus was induced by single intra peritoneal injection of STZ @ 50 mg/kg body weight in DCO and DSL group of rats. SLE was administered orally @ 100mg/kg body weight for 40 days to SCO and DSL groups. CON served as the negative control. Blood samples were collected from experimental animals on zero, 20th, and 40th days of trial to study various biochemical parameters. Significantly (P<0.01) lower levels of total serum protein, and hepatic glycogen and significantly (P<0.01) higher serum glucose, total cholesterol, urea and creatinine levels were observed in DCO group in comparison to CON group. However, in SLE treated diabetic rats (DSL group) significant (P<0.01) improvement was observed in all the above parameters. It may be concluded that SLE exerts ameliorative effect over Diabetes mellitus induced biochemical alterations in Wistar rats.