Diabetes mellitus is a metabolic disorder resulting from necrosis of β-cell and insulin resistance at the cellular level. Musa sapientum has been shown to possess anti-diabetic properties, however, the mechanism of its action is unknown. The effect of Methanolic extract of Musa sapientum leaves (MEMSL) and its fractions were assessed for in vitro inhibitory activity of α-amylase enzyme, in vivo hypoglycemic properties and liver glycogen content in alloxan-induced diabetic rats. Dried plant powder of Musa sapientum was successively extracted using n-hexane, ethyl acetate, dichloromethane and methanol respectively. The filtrate obtained was evaporated using rotary evaporator and the extract was stored at 4°C until use. The methanolic extract obtained was further fractionated using column chromatography. In vitro alpha amylase inhibitory activity of the methanolic extract at different doses (2.5mg/ml, 5mg/ml, 10mg/ml, 25mg/ml and 50mg/ml) and column fractions (100ug/ml) were assessed and compared with that of acarbose (5mg/ml), a standard oral α-amylase inhibitor. Hypoglycemic activity and liver glycogen content was studied using alloxan -induced diabetic male rats treated with MEMSL (250mg/kg and 500mg/kg), column fractions F2 and F5 (100μg/kg) for 14 days respectively. Results obtained showed a dose -dependent increase in α-amylase inhibitory activity of the methanolic extract at 5, 10, 25 and 50mg/ml exhibiting 29%, 61%, and 72% and 80% inhibitory activities respectively. Column fractions 2 and 5 showed the highest α-amylase inhibitory activity of 79% and 74% respectively. The MEMSL at 250mg/kg and 500mg/kg exhibited 66% and 59% hypoglycemic activities respectively compared with diabetic controls. Fractions 2 and 5 showed 48% and 75% reduction in blood glucose level respectively. Liver glycogen in diabetic animals treated with MEMSL (250mg/kg and 500mg/kg), F2 and F5 were significantly increased (5.5±0.5, 5.9±0.7, 3.6±0.5, 8.0±0.4 mg/100gwt. liver) compared with Diabetic controls (1.2±0.3 mg/100gwt. liver) respectively suggesting an increase in glucose storage or reduction in glycogen breakdown. It seems possible that the anti-diabetic properties in the leaf extract of Musa sapientum and its fractions maybe due to the inhibition of α-amylase, increased storage of glucose as glycogen in the liver and/or reduced breakdown of liver glycogen stores.