Ruellia tuberosa Linn belongs to family acanthaceae is a large sized plant distributed throughout India, Srilanka and Nepal. The aim of the present study was to evaluate the anti diabetic potential of methanolic extract of Ruellia tuberosa linn leaves in normal and alloxan induced diabetic rats. The Preliminary phytochemical screening shows the presence of carbohydrates, glycosides, phytosteroids, flavonoids, tannins, fixed oils & fats. Diabetes was induced in Albino rats by administration of alloxan monohydrate (150mg/kg, i.p).The methanol extract of Ruellia tuberosa linn leaves at a dose of 100 and 200mg/kg of body weight was administered at single dose per day to diabetes induced rats for a period of 14 days. The effect of methanol extract of Ruellia tuberosa linn leaves on blood glucose, serum lipid profile [total cholesterol (TC), triglycerides (TG), high density lipoprotein – cholesterol (HDL-C), low density lipoprotein – cholesterol (LDL-C), very low density lipoprotein – cholesterol (VLDL-C) and serum protein, albumin, globulin, serum enzymes [serum glutamate pyruvate transaminases (SGPT), serum glutamate oxaloacetate transaminases (SGOT), alkaline phosphatase (ALP)], were measured in the diabetic rats. The methanol extract of Ruellia tuberosa linn leaves elicited significant reductions of blood glucose (P<0.05), lipid parameters except HDL-C, serum enzymes and significantly increased HDL-C at the dose of 200mg/kg was compared with the standard drug Glibenclamide (5gm/kg). From the above results, it is concluded that methanol extract of Ruellia tuberosa linn leaves possesses significant antidiabetic, antihyperlipidaemic and hepatoprotective effects in alloxan induced diabetic rats.