Renal cell carcinoma (RCC) is the most lethal of all genitourinary malignancies. NEDD9/HEF1/Cas-L is a member of the Cas protein family and is known as a biomarker in multiple cancer types. In this study, we demonstrate for the first time that NEDD9 was upregulated in RCC tissue and cell lines. Immunohistochemical analysis and quantitative RT-PCR analysis showed low expression of NEDD9 in normal renal tissues and high expression in RCC tissues. In addition, in vitro experiments show that expression of NEDD9 was upregulated in RCC cell lines. Through MTT assay, we observed that NEDD9 knockdown inhibited cell proliferation. Furthermore, flow cytometry analysis showed that NEDD9 downregulation induced apoptosis. Together, our data suggest that abnormal NEDD9 protein expression may be a marker for RCC, and NEDD9 knockdown suppresses cell growth.