Background: Oxidative stress plays an essential role in bone health among postmenopausal women. This study aimed to compare the oxidative stress biomarkers among postmenopausal women aged 50–65 years with normal bone mineral density, osteopenia, and osteoporosis. Methods: In this observational study, 120 women with normal bone mineral density, 82 with osteopenia, and 86 with osteoporosis were selected based on the densitometry data obtained from the dual-energy X-ray absorptiometry method. The serum total antioxidant capacity (TAC), superoxide dismutase (SOD) activity, and malondialdehyde (MDA) levels were measured using biochemical methods. A binary logistic regression model adjusted for confounders was used to estimate the risk of osteopenia and osteoporosis. The P-value of <0.05 was considered statistically significant. Results: There were significant differences between the three groups in age, menopausal age, body mass index, and education (P<0.05). According to the binary logistic regression model, higher SOD activity and serum TAC levels were associated with a lower risk of osteoporosis (adjusted odds ratio [aOR], 0.991; 95% confidence intervals [CI], 0.986 to 0.996; and aOR, 0.373; 95% CI, 0.141 to 0.986, respectively). MDA was a significant risk factor for osteopenia in postmenopausal women (aOR, 1.702; 95% CI, 1.125 to 2.576). Conclusion Higher SOD activity and serum TAC levels in the studied postmenopausal women were associated with a significantly lower risk of osteoporosis. Moreover, the risk of osteopenia increased significantly with higher serum MDA levels.