Background <p>Osteoporosis (OP) frequently occurs in post-menopausal women, increasing the risk of fracture. Early screening OP could improve the prevention of fractures.This study focused on the significance of miR-208a-3p in diagnosing OP and development regulation, aiming to explore a novel biomarker and therapeutic target for OP.</p> Methods <p>The study enrolled a total of 154 post-menopausal women and grouping was performed based on the incidence of OP and fracture. The significance of miR-208a-3p was evaluated from the perspectives of menopausal correlation, OP diagnosis, and fracture prediction. In mechanism, the regulatory effect and mechanism of miR-208a-3p on osteoclast activation was investigated.</p> Results <p>miR-208a-3p was menopause-related showing a negative correlation with E₂ and positive correlations with FSH and LH. Significant upregulation of miR-208a-3p was observed in post-menopausal women with OP and showed significant diagnostic potential. Increasing miR-208a-3p was positively correlated with bone metabolism markers and negatively correlated with BMD of post-menopausal women with OP. Moreover, miR-208a-3p was also identified as a risk factor for fracture. STC1 was identified as a direct target of miR-208a-3p and was negatively regulated by miR-208a-3p. Silencing miR-208a-3p significantly alleviated macrophage inflammation and osteoblast activation, which was reversed by the knockdown of STC1.</p> Conclusion <p>Serum miR-208a-3p served as a diagnostic biomarker for OP and a risk factor for fracture in post-menopausal women. miR-208a-3p regulated macrophage inflammation and further mediated osteoclast activation via targeting STC1.</p>