Background/Aims: Giant cell tumor of bone (GCTB), one of the most common primary bone tumors, leads to extensive bone destruction. However, the mechanisms underlying GCTB progression remain elusive and prognostic factors and treatment targets are required. In the current study, we explored the function of the chemokine family member CCL20 in GCTB progression. Methods: We explored the expression of CCL20 in stromal cells (GCTSCs) using microarray. Clinical analyses of the role of CCL20 in tumor progression were performed based on the patient cohort of our institution. The role of CCL20 in tumor proliferation was evaluated by MTS assay, migration ability was measured by a Transwell assay, and osteoclastogenesis was induced by CCL20 or GCTSC-conditioned medium. Quantitative PCR and western blot were used to measure the expression levels of mRNAs and proteins related to tumor progression. Results: CCL20 was upregulated in GCTSCs and correlated with tumor progression and prognosis. CCL20 induced GCTSC proliferation and migration in an autocrine manner. In addition, CCL20 recruited mononuclear cells and induced osteoclastogenesis by overactivating the AKT and NF-κB signaling pathways. Antibody blockade of CCL20 abolished the exacerbated osteoclastogenesis. Conclusion: Taken together, our data indicate that GCTSC secretion of CCL20 acts as a key modulator in the pathological progression of GCTB. It can promote GCTSC proliferation and migration in an autocrine manner and can recruit bone marrow monocytes to the tumor microenvironment and enhance osteoclastogenesis in a paracrine manner. These findings strongly indicate the potential prognostic and therapeutic value of CCL20 in GCTB.