The risk of osteoporosis is higher in postmenopausal women and nutritional factors reported playing an important role in the etiology of low bone mineral density (BMD). Some studies claimed the involvement of vitamin B12 in the quality of bone structure in humans, however, results are not conclusive. The objective of this study was to explore the relationship between BMD and vitamin B12 levels in postmenopausal women. In this cross-sectional study, BMD and blood samples from 77 postmenopausal women (age > 45 years) were studied. BMD and T-scores of the study subjects were determined at the femoral neck and lumbar spines by Dual Energy X-ray Absorptiometry (DEXA). Serum VitB12 was measured by enzyme-linked immunosorbent assay. The mean±SD age of the postmenopausal women was 56.4±7.9 years. Bone mineral densities (g/cm2) were 0.80±0.16, 0.76±0.18, 0.74±0.14 and T-scores were -2.21±1.45, -1.41±1.22, -1.53±1.20 respectively at the lumbar spine, right femoral neck and left femoral neck. The mean±SD of vitB12 was 245.9±274.3 pg/mL. On multiple regression analysis, β values for log(VitB12) with BMD were 0.119 (p = 0.018), 0.085 (p = 0.140), 0.011 (p = 0.012) and with T-score were 1.028 (p = 0.022), 0.698 (p = 0.064), 0.940 (p = 0.015) at the lumbar spine and right femoral neck and left femoral neck respectively. In conclusion, vitamin B12 is found to be positively associated with bone mineral density and T-score at the lumbar spine and left femoral neck but not at the right femoral neck in postmenopausal women.