Aim:The aim of the present study was to find the effect of ethanolic extract of the whole plant of Portulaca oleracea on blood glucose levels and on body weight of streptozotocin induced diabetic rats. Methods: Rats were made diabetic by single dose of streptozotocin (50 mg/kg b.w).After checking their blood glucose levels, they were re-grouped into five groups. The 1 st group was Normal Control group,2 nd group was Diabetic Control group,3 rd group received standard drug Glibenclamide,4 th group received 50 mg.kg b.w of ethanolic extract of Portulaca oleracea and 5 th group received 100mg/kg b.w of the ethanolic extract of the plant. Their blood glucose levels and body weights were checked at regular intervals. Histopathology of pancreas of diabetic rats was also done. Results: The two doses of the ethanolic extract of the plant showed significant decrease in blood glucose levels and increase in body weights. Histopathological studies also showed significant changes. Discussion: Today diabetes mellitus is taking the form of the epidemic in many countries including India. Though conventional treatments are used to cure diabetes mellitus , but due to side effect of these drugs, there is need for alternative ways to cure the disease.Conclusion: The ethanolic extract of Portulaca oleracea has beneficial effects on blood glucose levels as well as improving other metabolic aberrations.