Abstract The acclaimed traditional use of vegetables as antidiabetic remedies has now been considered as one of the two basic diabetes mellitus control factors: food and medication. Allium species such as Allium cepa (onion, Hausa:Albasa) has attracted particular attention of modern medicine because of its widespread health use. In the present study the antidiabetic (hyperglycemic) potential of ethanol extract of cooked, dried and pulverized Allium Cepa bulbs was assessed in alloxan-induced diabetic mice. Hyperglycemia was induced by the injection of 150 mg/kg (i.p.) of alloxan monohydrate freshly dissolved in physiological saline. Doses (150, 450 and 750 mg/kg) per os, of the extracts were separately administered to a group of five diabetic mice in the study. The activity was compared with reference standard glibenclamide (2 mg/kg, p.o.) and negative control of physiological saline. Treatment of the alloxan-induced diabetic mice with the ethanol extracts of Allium cepa decreased the raised blood glucose levels significantly (P< 0.05) in a dose-dependent manner. Results of phytochemical screening of the ethanol extracts of cooked Allium cepa bulb have indicated the presence of cardiac glycoside, steroids, terpenoids, alkaloids, flavonoids, and anthraquinones. Moreover, some of the phytochemicals observed in this plant extract have previously been observed to contribute to hyperglycemic effects.