Background and aim of the study- Diabetes is a chronic metabolic disease which affects large number of population all over the world. More than 400 traditional medicinal plants have been recorded for helping in controlling such disease. This study investigated effects of some plants used in Saudi Arabia and some other Arab countries as antidiabetic agents. Materials and Methods: One hundred fifty adult male Albino rats were divided into six experimental groups each consist of twenty five rats. The first group was considered as a control group. The rest of groups were affected by induction of experimental diabetes by subcutaneous injection of Alloxan. The second group consisted of diabetic rats without any treatment. The third group was treated by the aqueous extract of mixture contains Foenugreek, Nigella and Termis seeds. The fourth group was treated with the aqueous extract of Nigella sativa seeds, while the fifth group was treated with the aqueous extract of Foenugreek seeds.The sixth one was treated with the aqueous extract of Termis seeds with the administered dose of the plant extracts (100 mg/kg body weight).After four weeks of treatment, different biochemical parameters were performed including estimation of blood sugar level and serum insulin level. Pancreatic and liver samples were obtained and processed for microscopic and quantitative evaluation after staining the prepared sections with both heamatoxylin and eosin as well as a special stain for demonstration of the different pancreatic cells in the Islet of Langerhans. Results: The usage of the mixture or each plant alone corrected the glucose level and insulin level. Microscopically there was definite decrease in the number and diameter of beta pancreatic cells in the diabetic group, while the other pancreatic cells were not affected (alpha and delta cells). The use of medicinal plants in the different groups of this study greatly improved such cellular changes and the level of blood sugar level was corrected. The present results showed that the activity of the mixture was the best when compared with Nigella, Foenugreek and Termis seeds. Conclusions: The water extract of the mixture is the most powerful in amelioration hyperglycemia and most of all damage effects of Alloxan on the liver and texture, hematological parameters, and lipid profile. So it is advised to use the plant mixture as an antidiabetic agent rather than the use of each plant separately. Repeating such study with the use of variable doses may be helpful in better evaluation for the required doses.