This study investigated both morphologically and biochemically whether parsley (Petroselinum crispum), which is used as a folk remedy to decrease blood glucose, has any antidiabetic effect on pancreatic B cells of rats. Parsley extract was given to male diabetic rats. In the diabetic group given parsley extract, it was detected that the number of secretory granules and cells in islets and other morphologic changes were not different from the control diabetic group, while the blood glucose levels in the diabetic group given the plant extract were reduced in comparison to the diabetic group. In addition, a decrease was observed in the weight of the control diabetic group and the diabetic group given the plant extract. It is suggested that the plant therapy can provide blood glucose homeostasis and cannot regenerate B cells of the endocrine pancreas.