This study was carried out to investigate serum superoxide dismutase (SOD) activity and malondialdehyde concentration of albino rats fed ethanol leaf extract of Annona muricata. Fifteen (15) wistar albino rats were divided into 3 groups of five each. Group one animals served as the normal control group, which was administered normal saline, group two and three were administered 200 mg/kg and 400 mg/kg of ethanol leaf extract of Annona muricata respectively for one week (7days). The result showed a slight increase in superoxide dismutase activity of the rats that were administered 200 mg/kg of the extract when compared to the control group. For group three administered with 400 mg/kg of the extract, there was also a slight increase in the activity of SOD when compared to the normal control but lower than the 200 mg/kg group. For malondialdehyde (MDA) it was observed that the MDA concentration decreased in group three which received 400mg/kg doses of the extract when