Diabetes mellitus is a metabolic disorder characterized by increasing level of blood (hyperglycemic) due to impaired insulin secretion and the increase of insulin resistance. The research aimed at finding out the effectiveness of Mahogany leaves' ethanol fraction (Swieteniamacrophylla King) in lowering the blood glucose level of male white rats which have been induced glucose. The rats were divided into five treatment groups, i.e. negative control group (NaCMC 0,5%), positive control group (Glibenclamide), Mahogany leaves' ethanol fraction group dosage 50, 100, and 200 mg/kgBW. Blood was taken from the tail veins at the 0, 30, 60, 90, 120 and 150 minute, calculated from the time when glucose was given. Based on the mean of obtained blood glucose level, the value of AUC0-150 can be calculated. AUC0-150 data was analysed by using One Way ANOVA statistic test continued by LSD test. The analysis result showed that there was a significant difference (p<0,05) among negative control group with positive control group as well as mahogany leaves' ethanol fraction treatment group. The blood glucose decreased percentage of the leaves ethanol fraction dosage 50, 100, and 200 mg/kgBW showed that the blood glucose decreased effects were 41.52; 42.85; and 47.94%.