Mimosa pigra is used in traditional medicine to lower blood glucose in diabetic patients. The objective of this study was to evaluate the antihyperglycaemic activity of the ethanol root extract of Mimosa pigra in albino rats. The rats were divided into five groups, each containing five rats. Group 1 served as the normal control (non-diabetic), groups II and III were treated with 250mg/kg and 500mg/kg of the ethanol extract of Mimosa pigra respectively, group IV was treated with glibenclamide and group V, the diabetic control group was untreated. Diabetes was induced through intraperitoneal injection of 160mg/kg alloxan monohydrate. Preliminary phytochemical screening of the ethanol extract revealed the presence of steroids (triterpenes), tannins, flavonoids, phlobatannins, and saponins. The LD50 was found to be greater than 5000mg/kg In the acute study, the 250mg/kg extract showed a reduction in the blood glucose level at the 6th hour which was statistically significant (P<0.05) compared to the diabetic control group, while the 500mg/kg extract showed no statistically significant reduction (P<0.05) compared to the diabetic untreated animals. In the prolonged study, on days 1, 3, 7, 10, the 250mg/kg extract showed a statistically significant reduction in blood glucose level compared to the diabetic control group, while the 500mg/kg extract showed a reduction in blood glucose levels on days 1, 3, 5 which was statistically significant (P<0.05) compared to the diabetic control group. The results suggest that extract of the root of Mimosa pigra possess significant anti-diabetic activity.