Abstract: Medicinal plants play a major role in the management of Diabetes mellitusespecially in developing countries. The present study investigated the possible protective effects of hexane extract of Cassia fistula bark on certain biochemical parameters in Streptozotocin (STZ) induced diabetes in rats. Cassia fistula (Caesalpinaceae) has been used in traditional medicine. The barks of C. fistula have already been scientifically proved to possess anti-oxidant properties. The hypocholesterolemic and hypoglycemic effects of the hexane extract of stem bark of C. fistula, in normal and streptozotocin induced diabetic rats, were investigated in the present study. Hexane extract of C. fistula bark at doses 0.15, 0.30, 0.45 g kg-1 body weight for 30 days suppressed the elevated blood glucose levels in diabetic rats. The extract at 0.45 g kg-1 was found to be comparable with glibenclamide, the reference drug. The lipid profile (total cholesterol, triglyceride, HDL-cholesterol, LDL and VLDL-cholesterol) after the extract treatment at 0.45 g kg-1 body weight showed remarkable improvement compared to the diabetic control animals. Antioxidant and polyphenol content present in the extracts might contribute to the antihyperglycemic and antilipidemic properties. Thus the results suggest that Cassia fistula barks would be effective in the treatment of diabetes and in prevention and management of coronary artery disease.