Abstract: The aim of this study was to evaluate the effects of essential oil extracted from aerial parts of Artemisia sieberi in normal and alloxan induced diabetic rats. Fifty rats were divided into five groups of 10 each. Group I normal rats received 1 mL day-1 of dimethyl sulfoxide (control); group II normal rats received a single dose (80 mg kg-1 b.wt.) of essential oil extract of Artemisia sieberi; group III diabetic rats received 1 mL day-1 of dimethyl sulfoxide; group IV diabetic rats received the oil extract (80 mg kg-1 b.wt.); group V diabetic rats received metformin (14.2 mg kg-1 b.wt.). All treatments were orally administered once a day for six weeks. Changes in blood glucose concentration, body weight and food and water intake were measured and the data obtained were compared with that of metformin. The essential oil extract significantly (p<0.05) lowered blood glucose level as well as food and water intake in diabetic rats accompanied by an increase in body weight gain with no apparent side effect when compared with untreated diabetic rats. These effects were found to be closely similar to that of metformin, a common antidiabetic drug. On other hand, no apparent improvement on body weight gain in diabetic rats treated with metformin. In addition, for all parameters measured, the oil extract showed no effect in normal rats. In conclusion, the essential oil of Artemisia sieberi exhibited antidiabetic activity in alloxan-induced diabetic rats. Present findings support the possible use of the essential oil of Artemisia sieberi as a remedy for diabetes mellitus in humans.