Coumarin compounds own different type of biological activities like antimicrobial, anti-inflammatory and anti-diabetic. The present study undertaken to investigate anti-diabetic activity of new synthetic coumarin derivatives in alloxan-instigated diabetic rats. Effect of coumarins on normal rats studied. Diabetes persuade in Wistar rats by injecting alloxan hydrate (150 mg/kg, body weight) once. Normoglycemic and hyperglycemic rats separated into different groups. Animals treated with coumarins & Metformin (100mg/kg) as a reference drug for a period of 21 days. Antidiabetic activity assessed by measuring blood glucose, insulin, lipid profile, total proteins and calcium. Coumarin derivatives (200 mg/kg) treatment for 21 days exhibited very little anti-diabetic activity as compared with the standard drug metformin (100mg/kg) treatment. Alloxan made diabetic rats treated with coumarins (200 mg/kg) showed non-significant reduction in serum glucose, total cholesterol, triglycerides, but serum HDL- cholesterol, total proteins and calcium were significantly decreased. Coumarin derivatives do not possess effective anti-diabetic property. Because, treatment with these synthetic compounds there is no significant reduction in blood glucose level and lipid profile not corrected and slightly increase in the level of serum protein and calcium seen in alloxan induced diabetic rats.