This study was designed to determine the effects of methanolic extracts of Annona muricata (Linn) on the blood glucose level of streptozotocin-induced diabetic Wistar rats. Thirty adult Wistar rats were randomly assigned into three groups (A, B and C) of ten rats each. Group A was the control, Group B was untreated hyperglycemic group and group C was A. muricata-treated group. Hyperglycemia was induced in groups B and C by a single intraperitoneal injection of 80 mg/kg streptozotocin dissolved in 0.1 M citrate buffer. The control group was intraperitoneally injected with equivalent volume of citrate buffer and all the animals were monitored for four weeks. Daily intra peritoneal injection of 100 mg/kg A. muricata was administered to group C rats for two weeks and the animals were monitored for another two weeks. The data obtained were analyzed with descriptive and inferential statistics. The result showed a mean body weight of 206 +/- 7.74 g, 173.29+/-5.13 g and 197 +/- 5.62 g respectively for the control, untreated diabetic and A. muricata-treated diabetic group, and a mean blood glucose concentration of 3.78 +/- 0.190 mmol/L, 21.64 +/- 2.229 mmol/L and 4.22 +/- 0.151 mmol/L for the control, untreated diabetic and treated diabetic groups respectively. A significant difference exists between the blood glucose concentrations of treated and untreated hyperglycemic groups of rats. The result of this study demonstrated that A. muricata possesses anti-hyperglycemic activities.