Diabetes mellitus is a major global metabolic disorder of current century. Plants represent a vast source of potentially useful dietary supplements for improving blood glucose control and preventing long-term complications in type 2 diabetes mellitus. This study was undertaken to investigate the microscopic characteristics of Momordica charantia fruits and phytochemical analysis of extracts. Glucose tolerance test, hypoglycemic, antidiabetic effect, serum lipid profile and histopathological studies of pancreas, kidney and liver in normal control rats, diabetic control rats and extract treated rats were also carried out for single and repeated oral administration of the aqueous extract of Momordica charantia (Family: Cucurbitaceae) fruits in normal and alloxan induced diabetic rats. A range of doses, viz. 250 and 500 mg/kg b.w. of aqueous fruit extract of Momordica charantia were evaluated and the dose of 500 mg/kg was identified as the most effective dose. In acute studies it lowers blood glucose level around 42%after 3 h of administration and in sub-acute studies it showed 22% reduction in blood glucose level in normal rats. The same dose of 500 mg/kg produced a fall of 30% in blood glucose level within 90 min during glucose tolerance test (GTT) in normoglycemic rats. This dose has closer effect as that of standard drug glibenclamide (10 mg/kg b.w.). In diabetic rats in acute studies it lowers blood glucose level around 4%after 5 h of administration and in sub-acute studies it showed 39% reduction in fasting blood glucose level on 7th day.Total cholesterol (TC), low density lipoprotein (LDL), albumin and triglyceride (TG) levels also decreased in severely diabetic rats whereas, cardio protective, high density lipoprotein (HDL) and protein level in serum were increased. Concurrent histological studies of the pancreas of these animals showed comparable regeneration by aqueous extract and kidney and liver showed normal structure in the rats which were earlier, necrosed by alloxan. These results clearly indicate that aqueous extract of Momordica charantia has high antidiabetic potential along with significant hypoglycemic and antidiabetic effects. Further studies are warranted to fractionate the active principles and development of polyherbal formulations by using other traditional antidiabetic plant extracts and determination of its synergistic effects.