Withania coagulans and Psidium guajava are used for treatment of Diabetes mellitus. Both are compared for its actions onDiabetes mellitus. Withania coagulans and Psidium guajava arecollected and authenticated.Physico-chemical Parameters of both herbs have been presented. Successive solvent extraction of Withania coagulans and Psidium guajava were performed. Preliminary Phytochemical Examination shows the presence of Steroids, Saponin, Alkaloids, Flavonoids, glucoside and Tannins in various extracts.Pharmacological evaluations by In vivo oral glucose tolerance test indicate that aqueous extract of Withania coagulansreduced blood sugar level significantly as compared to aqueous extract of Psidium guajava. In vivo anti diabetic activity was performed using Streptozotocin induced diabetic rats.10 mg of glipizide produced 70% reduction in blood sugar level,1106 mg of aqueous extract of Withania coagulans and 1193 mg of aqueous extract of Psidium guajava alsoproduced 70% reduction in blood sugar level. Thus, 10 mg of glipizide is equivalent to 1106 mg of aqueous extract of Withania coagulants and also equivalent to 1193 mg of aqueous extract of Psidium guajava. Withania coagulans is more potent than Psidium guajavafor diabetic patients in controlling their blood glucose level.