Diabetes mellitus is a group of metabolic disorder in which blood sugar levels are abnormally high over a prolonged period. Drug treatment for diabetes mellitus is expensive and carries risks for many adverse effects. Moreover, continuous use of synthetic antidiabetic drugs causes side effects and toxicity. Therefore, there is a need for natural and non-toxic antidiabetic drugs for diabetic therapy. The study was performed to investigate the blood glucose lowering effect of mahogany (Swietenia macrophylla King) leaves in experimentally induced diabetic rats. The ethanolic, ethyl acetate, and petroleum eter fraction of mahogany leaves were tested to male rats that had previously been induced glucose (6.75 g/kg body weights). The rats were divided into five Groups (Group I-V). Control animals received only standard rat food as Group. Group II rats were given glibenclamide orally at a dose level 1 mg/kg body weight as positive control. Group III-V received extract of mahogany leaves at dose 50, 100, and 200 mg/kg body weight, respectively. Blood glucose level was observed on 30, 60, 90, and 120 hours after treatments. The results provide information that the ethanolic, ethyl acetate, and petroleum eter fraction of mahogany leaves has potent antidiabetic activity in glucose induced diabetic rats.