Deubiquitinases (DUBs), frequently overactivated in cancers, are associated with tumorigenesis and regarded as promising therapeutic targets. However, the underlying mechanism of DUBs promoting non-small cell lung cancer (NSCLC) are poorly understood. Through a global analysis of the contribution of 97 DUBs in NSCLC survival possibilities by The Cancer Genome Atlas (TCGA) database, we found that high expression of Josephin Domain-containing protein 2 (JOSD2) predicted the poor prognosis of patients. Depletion of JOSD2 significantly impeded NSCLC growth in vivo in both cell/patient-derived xenografts. Mechanistically, JOSD2 inhibits LKB1 kinase activity by removing K6-linked polyubiquitination, which was critical for maintaining LKB1-STRAD-MO25 complex integrity. Furthermore, we identified the first small molecule inhibitor of JOSD2 and the pharmacological inhibition of JOSD2 significantly arrested NSCLC proliferation in vitro/in vivo. Notably, our findings demonstrate a crucial role of JOSD2 in hindering LKB1 activity, highlighting JOSD2 as a potential therapeutic target in NSCLC and providing its inhibitors as a promising strategy for NSCLC treatment.