Abstract: Objective To investigate the expression and clinical significance of ubiquitin-specific protease 9X (USP9X) protein in non-small cell lung cancer (NSCLC). Methods USP9X proteins were detected in 71 cases of NSCLC and 20 cases of benign pulmonary tissues by immunohistochemical staining. The correlation between USP9X expression and 51 NSCLC clinicopathological parameters as well as survival rates were indicated. Results Higher rate 〔69.0% (49/71)〕 of the expression of USP9X was observed in NSCLC samples, compared with 20.0% (4/20) in benign pulmonary tissues (P<0.001). Furthermore, the expression of USP9X proteins was positively associated with both histological types and lymph node metastasis (P<0.05). The survival analysis showed that the survival rate was lower in patients with positive expressions of USP9X than in patients with negative expressions (P<0.05). USP9X expression, together with histological types and TNM stage was an independent predictor for overall survival in the multivariate Cox regression model (P<0.05). Conclusion Up-regulation of USP9X plays an important role in the invasion and progression of NSCLC and could be considered as a prognostic predictor for NSCLC.