[Purpose] Osteoporosis is an inflammatory disease, and platelets play a critical role in bone remodeling. Mean platelet volume has been shown to be influenced by inflammation. Our aim was to evaluate the relationship between mean platelet volume and bone mineral density in postmenopausal women. [Subjects and Methods] The records of female patients who had been referred to a tertiary hospital for bone mineral density analysis were retrospectively reviewed. [Results] A total of 175 patients (mean age: 61.3 ± 9.0 years) were enrolled. Overall, 72% (126/175) of patients met the criteria for osteoporosis. Mean platelet volume was found to be inversely correlated with body mass index. There was a significant positive correlation between mean platelet volume and femoral neck bone mineral density in our normal weight osteoporotic group, whereas there was a significant negative correlation in our overweight-obese osteoporotic group. The negative correlation between mean platelet volume and femoral neck bone mineral density in the overweight-obese osteoporotic group persisted after adjustment for confounding factors. Multivariate analyses revealed that mean platelet volume was significantly associated with femoral neck bone mineral density in osteoporotic patients in both our normal weight and overweight-obese groups. [Conclusion] Regardless of mechanisms, mean platelet volume might be used as a biomarker for osteoporosis in clinical settings.