Osteosarcoma (OS) is the most common bone cancer in children and adolescents. Although the 5-year survival rate of most OS is more than 70%, it drops to 25% for those with recurrent or metastasized tumors. Furthermore, the standard care of OS has not changed in the past three or more decades, and there is no FDA-approved targeted therapy and immunotherapy for OS. Therefore, there is a great need to develop new therapeutic targets to reduce side effects and improve the prognosis for OS patients. The lack of targetable genetic alterations in OS suggests that transcriptional and epigenetic events are involved in the etiology of this deadly cancer type. The RUNX2 (RUNX family transcription factor 2) protein is one of the transcription factors (TFs) critical for the survival of OS cells, and it is highly expressed in OS cells and tumors. Thus, understanding the RUNX2-regulated transcriptional circuitry is essential for developing novel therapeutical strategies for OS. However, the transcriptional network related to RUNX2 in OS remains largely unclear. Using an integrated multi-omics approach (RNAseq, ChIPseq, and proteomics), I identify a dozen of transcription factors in the RUNX2-regulated transcriptional circuitry. Among these factors, I focused on SOX9 as a direct target of RUNX2 and assessed its function to promote OS cell survival by employing CRISPR-Cas9-mediated knockout. I found that depletion of SOX9 induced apoptosis in vitro and reduced OS tumor growth in vivo. To identify SOX9 downstream targets, I used RNAseq, ChIPseq, pathway analysis, and gene set enrichment analysis and found that SOX9 activated the transcription of MYC, a downstream target of RUNX2. To further explore the SOX9-regulated network in OS, BioID was carried out to identify the interactome of SOX9. Interestingly, SOX9 binds to RUNX2, suggesting a transcriptional network involving SOX9, RUNX2, and MYC. In addition, I identified the chromatin factor JMJD1C as a novel binding partner of SOX9, and the proximity ligation assay (PLA) confirmed the interaction between SOX9 and JMJD1C in OS cells. Because inhibitors of JMJD1C are being developed, my results reveal a possible targeting node regulated by SOX9 in the RUNX2-regulated transcriptional circuitry and are likely to contribute to developing targeted therapy for OS to overcome the current limitation in clinical trials.