TRAF6 regulates proliferation, apoptosis, and invasion of osteosarcoma cell. TRAF6, a unique tumor necrosis factor receptor-associated factor (TRAF) family member, possesses a unique receptor-binding specificity that results in its crucial role as the signaling mediator for TNF receptor superfamily and interleukin-1 receptor/Toll-like receptor superfamily. TRAF6 plays an important role in tumorigenesis, invasion and metastasis. This study aimed to explore the expression of TRAF6 in osteosarcoma tissues and its correlation to the clinical pathology of osteosarcoma and to discuss the relationship between TRAF6 expression and osteosarcoma invasion. These data will provide the experimental base for the biological treatment of osteosarcoma in the future. Using RT-PCR and Western blot, the results showed that the expression rate of TRAF6 mRNA in osteosarcoma tissues was significantly higher than that in normal bone tissue (p < 0.05), that the expression rate of TRAF6 mRNA in the carcinoma tissues from patients with lung metastasis was significantly higher than that from patients without lung metastasis (p < 0.05), and that the expression rate of TRAF6 mRNA also increased with increasing Enneking stage (p < 0.05). However, the mRNA expression of TRAF6 in osteosarcoma was independent of the patient's gender, age, and tumor size (p > 0.05). The TRAF6 protein displayed an up-regulation in osteosarcoma tissues compared to normal bone tissue (p < 0.05), displayed an up-regulation in osteosarcoma tissues from patients with lung metastasis compared to from patients without lung metastasis (p < 0.05), and displayed a gradual increase with increasing Enneking stage (p < 0.05). By the technique of RNA interference, the expression of TRAF6 in the human osteosarcoma MG-63 cell line was down-regulated, and the invasive ability of MG-63 cells was examined. The results showed that TRAF6 protein expression was significantly decreased in the MG-63 cells from TRAF6 siRNA-transfected group (p < 0.05), and the proliferation ability of MG-63 cells and the number of MG-63 cells that passed through the Transwell chamber were significantly lower than that in the non-transfected control group as well as the transfected control group (p < 0.05). In addition, the percentage of MG-63 cells undergoing apoptosis was significantly higher in the TRAF6 siRNA-transfected group compared with the non-transfected control group as well as the transfected control group (p < 0.05). The expression of p-p65, cyclin D1, MMP-9 was down-regulated in the MG-63 cells from TRAF6 siRNA-transfected group. The expression of caspase 3 was up-regulated in the MG-63 cells from TRAF6 siRNA-transfected group compared to the non-transfected control group as well as the transfected control group (p < 0.05). To make a long story short, the overexpression of TRAF6 in osteosarcoma might be related to the tumorigenesis, invasion of osteosarcoma.