The purpose of the current study was to assess in-vitro aldose reductase and the anti-diabetic properties of Murraya koenigii (MK) seeds on Streptozotocin (STZ)-induced diabetic rats. Methodology: The in-vitro antioxidant capacity of the prepared extract was compared with that of ascorbic acid. Then in-vitro aldose reductase activity of extract was assessed employing quercetin as a reference in rat lens and kidney tissue samples. This was followed by the in-vivo antidiabetic activity (200 mg/kg and 400 mg/kg body weight) of methanolic extract of Murraya koenigii (MEMK) seeds was carried out in STZ induced rats for a study period of 60 days. During this period, fasting blood glucose (FBG) levels were assessed. The serum parameters, anti-oxidant and urine parameters were all evaluated at the end of the study. The histopathological investigation was carried out on rat kidney, eye lens and pancreas. Results: Substantial in vitro antioxidant activity was detected for M. koenigii (MK) extract. Methanolic extract of MK showed significant in vitro inhibitory activity against aldose reductases in rat lens, kidney and human homogenate samples. In the antidiabetic study, the changes seen in the FBG levels, serum parameters, antioxidant levels, and urine parameters nearly returned to normal. Microscopic examinations of the pancreatic cells of STZ-induced diabetic rats revealed deterioration and atrophy. Inflammation in the ciliary muscles of the lens was seen in STZ-induced diabetic rats along with tubular dilatation, degeneration, and haemorrhages in kidney; these histopathological defects were delayed following administration of MK extract. The extract effectiveness was on par with that of the well-known hypoglycaemic medication glibenclamide. Conclusion: These results support in-vitro aldose reductase effect and antidiabetic effect of MK seeds and further studies to develop Nutraceutical from MK seed will be useful