Context: Most randomized and controlled studies that evaluated the effect of vitamin D (VD) supplementation on bone mass included the association with calcium, a fact that makes it difficult to identify the effects specifically attributable to VD. Objective: to evaluate the effect of supplementation of VD alone on the bone turnover markers in postmenopausal women. Methods: This is a double-blind, placebo-controlled trial. Serum levels of total calcium, parathormone(PTH), alkaline phosphatase(AP) and 24h-urine calcium were determined. Serum C-terminal telopeptide of type I collagen(s-CTX) and procollagen type 1 amino-terminal propeptide(P1NP) as markers of bone resorption and formation, respectively, were measured by immunoassay. Plasma 25(OH)D concentrations were measured by HPLC. Intention-to-treat analysis was performed using t-test, Gamma distribution, ANOVA and Tukey test. Participants: Women aged 50-65years with amenorrhea ≥12months and normal bone mineral density, were included. Those with previous use of VD or of drugs that could interfere with bone metabolism (bisphosphonate, estrogen, testosterone, corticosteroids, tamoxifen, calcitonin); primary hyperparathyroidism or hypercalciuria; renal failure; liver disorders were excluded. Interventions:The intervention time was 9months, with assessments at baseline and endpoint. A total of 160 postmenopausal women randomized into two groups: VD group, vitamin D3 supplementation 1,000IU/day/orally(n=80) or placebo group(n=80). Main Outcome Measures: Effect of isolated VD supplementation on bone turnover markers. Results: After 9 months, 25(OH)D concentrations increased from 15.0±7.5 to 27.5±10.4ng/ml in VD group and decreased from 16.9±6.7 to 13.8±6.0ng/ml in placebo group(p <.001). There was a decrease (-21.3%) of PTH values in VD group with a significant difference between groups at the end of the study(p <.001). No significant differences were observed in the other laboratory parameters (total calcium, AP, and calciuria) in either group(p >0.05). Comparison of bone turnover markers showed a significant reduction in s-CTX(-24.2%,p <.0001) and P1NP(-13.4%,p=0.003) levels in VD group. No significant variations in bone turnover markers were observed in the placebo group. Conclusion: In postmenopausal women with VD deficiency, isolated supplementation with 1,000IU of vitamin D3 for 9months associated with a reduction in bone turnover markers. Financial support from FAPESP, process no 2014/00001-0.