Non-small cell lung cancer (NSCLC) as the most frequently diagnosed lethal cancer remains the major cause of overall cancer-related death worldwide. Testes-specific protease 50 (TSP50) has been proved as a critical biomarker in various cancers, and we previously reported that TSP50 protein expression is overexpressed in clinical resected NSCLC tumor tissues and related to poor prognosis in NSCLC patients. Hence, the present study was designed to further investigate the potential oncogenesis mechanism of TSP50 in NSCLC cells. Real-time quantitative PCR, immunohistochemical assay and western blot analysis were used to analyze the TSP50 mRNA and protein expression in 20 NSCLC cases, and TSP50 expression was observed to have high levels in the NSCLC specimens and paired metastatic lymph node tissues when compared to the levels in corresponding normal lung tissues and normal lymph nodes. In the experiments in NSCLC cell lines, lentiviral short hairpin RNA (shRNA) delivery system was applied to knock down TSP50 in 95D cells, and the following investigations revealed that downregulation of TSP50 expression markedly reduced cell proliferation, colony formation and migration ability in vitro. Furthermore, the inhibition of TSP50 induced G0/G1-phase arrest and decreased expression levels of cell cycle relative markers CDK4, CDK6, and CyclinD1 and increased expression of p21 and p53 in 95D cells. In conclusion, this study indicates that TSP50 plays a significant role in NSCLC cell proliferation and may act as a novel oncogene in the development and progression of NSCLC, offering a potential cancer therapeutic target for the treatment of NSCLC.