The preferentially expressed antigen of melanoma (PRAME), a cancer-testis antigen with unknown function, is expressed in many human malignancies and is considered an attractive potential target for tumor immunotherapy. However, studies of its expression and function in osteosarcoma have rarely been reported. In this study, we found that PRAME is expressed in five osteosarcoma cell lines and in more than 70% of osteosarcoma patient specimens. In addition, an immunohistochemical analysis showed that high PRAME expression was associated with poor prognosis and lung metastasis. Furthermore, PRAME siRNA knockdown significantly suppressed the proliferation, colony formation, and G1 cell cycle arrest in U-2OS cells. Our results suggest that PRAME plays an important role in cell proliferation and disease progression in osteosarcoma. However, the detail mechanisms of PRAME function in osteosarcoma require further investigation.