An experiment was conducted to evaluate the effect of feeding orange pulp on plasma antioxidant status and bone quality in orchidectomized rats. Forty-five one-year-old male rats were randomly placed in a sham-control group and four orchidectomized groups. Orchidectomized rats were assigned to one of the following treatments: orchidectomy (ORX), ORX+2.5% orange pulp (OP); ORX+5.0% OP; ORX+10.0% OP. Four months after the study began, all rats were killed, blood was collected, and the plasma was harvested for antioxidant status and IGF-I. Orchidectomy did not (P > 0.1) affect red blood cell hemolysis percentage, but decreased (P < 0.05) the plasma IGF-I concentration, bone density, femoral strength, time induced femoral fracture, calcium and magnesium concentrations in the femur and the 5th lumbar, and increased (P < 0.05) urinary deoxypyridinoline, calcium and magnesium excretions compared to the sham group. Feeding 2.5% OP tended to increase IGF-I and increased (P < 0.05) bone density, femoral strength, and time induced femoral fracture. Feeding 10% OP profoundly (P < 0.05) improved antioxidant status by protecting red blood cells against hemolysis, increased (P < 0.05) the plasma IGF-I, bone density and bone mineral content, and decreased (P < 0.05) urinary magnesium excretion and urinary deoxypyridinoline concentration. In conclusion, orange pulp significantly affects bone quality by enhancing calcium and magnesium deposition in bones and by slowing-down bone turnover rate.