Purpose <p>Gut microbiota has been implicated in bone health. However, the extent of the skeletal benefits of probiotic supplementation in humans remains unclear. A systematic review and meta-analysis was performed to appraise the efficacy of probiotic supplementation in improving bone health through a comprehensive qualitative and quantitative synthesis of the available randomized controlled trials.</p> Methods <p>The PubMed, Web of Science, and China National Knowledge Infrastructure databases were searched for RCTs reporting the effects of probiotic supplementation on bone mineral density (BMD), C-terminal telopeptide of type 1 collagen (CTX), or procollagen type 1 N-propeptide (P1NP). A random-effects model was used to generate the pooled weighted mean differences and 95% confidence intervals.</p> Results <p>Probiotic supplementation significantly increased lumbar spine aBMD (areal BMD) (+ 0.010; <i>n</i> = 16) and hip aBMD (+ 0.022&#xa0;g/cm²; <i>n</i> = 9) but had no significant effect on femoral neck aBMD (<i>n</i> = 7), P1NP (<i>n</i> = 10), and CTX (<i>n</i> = 11). Low-to-high heterogeneity was present in all analyses, likely due to differences in participant and intervention characteristics. A tendency toward increased lumbar spine aBMD was observed across subgroups, although statistical significance was not always reached, while findings for other outcomes varied. Most trials included postmenopausal women, and restricting the analyses to this population yielded results consistent with the main analyses. The increase in lumbar spine aBMD remained significant regardless of trial exclusion, whereas the effect on hip aBMD became non-significant when key trials were omitted. </p> Conclusion <p>Based on the evidence from the currently available RCTs, probiotic supplementation appears to lead to modest but statistically significant improvement in lumbar spine BMD and, to a lesser extent, hip BMD in postmenopausal women.</p>