This study examined the protective effect of Allium cepa extract from red onion on aluminuminduced anemia in female wistar rats. Twenty-four animals (six rats per group) were used for this study. They were divided into four groups: group one served as control, group two animals were treated with 100mg/kg BW of aluminum chloride and served as Aluminum chloride (AlCl3) group, group three, Allium cepa alone group were treated with 1mL/100g BW of Allium cepa while group four was simultaneously treated with 1mL/100g BW of Allium cepa and 100mg/kg BW AlCl3. Treatments lasted for 4 weeks. Red blood cells (RBC), packed cell volume (PCV), Hemoglobin concentration (Hb) were measured from blood sample collected from each rat. Serum urea, serum and kidney malondialdehyde (index of lipid peroxidation) and kidney catalase and superoxide dismutase (SOD) activities were measured spectrophotometrically. Significant decrease in RBC, PCV, Hb, catalase, SOD and significant increase in serum urea and malondialdehyde were observed in aluminum treated animals when compared with control. Animals treated with Allium cepa alone had significant increase in PCV, Hb, SOD and significant decrease in malondialdehyde and serum urea while there was no significant different in RBC and catalase when compared with control. Simultaneous treatment of the animals with Allium cepa and aluminum chloride resulted in significant increase in PCV while there was no significant different in RBC, Hb, catalase, malondialdehyde when compared with control.This study reveals that Allium cepa extract treatment ameliorate aluminum-induced anemia through antioxidant system.