The preventive effect of the hydro-alcoholic extracts of Artemisia herba-alba Asso (AHA), and Centaurium erythraea Rafn (CE), two medicinal plants used in traditional treatment of diabetes in the north-eastern Algeria, were evaluated in animal models of type 2 diabetic induced with a standardised high fat diet (HFD).Plant extracts were administered orally by gavage at a dose of 2g/kg bodyweight daily for 20 weeks to male C57BL/6J mice fed HFD. Animals were weighed and plasma glucose measured weekly and insulin at the end of study using standard ELISA methods.After 6 weeks, blood glucose levels increased in HFD control mice. At end of study (20 weeks) in groups treated with AHA or CE extracts vs. HFD control group there was a significant reduction in mean (±SD) fasting blood glucose (respectively 108.0±42.0 and 120.4±45.1 vs. 183.1±19.1mg/dl, p<0.05), triglyceride concentrations (26.9±6.7 and 27.9±17.8 vs. 48.9±12.1mg/dl, p<0.05) and serum insulin levels (1.1±1.0 and 0.6±0.7 vs. 3.1±1.8ng/ml, p<0.05). Plant extracts also markedly reduced insulin resistance as measured by the homeostasis model assessment (HOMA) compared to HFD controls (AHA: 4.4±5.3, CE: 3.0±3.3 vs. HFD control 38.3±26.6, p<0.05). The plant extracts had no effect on calorie intake or body weight.AHA had been shown to have a hypoglycaemic effect in diabetes but this is the first demonstration of a preventive effect of AHA and CE on HFD-induced diabetes.