<p>5-methylcytosine (m5C) methylation is a post-transcriptional modification of RNAs, and its dysregulation plays pro-tumorigenic roles in lung adenocarcinoma (LUAD). Here, this study&#xa0;elucidated the mechanism of action of NSUN2, a major m5C methyltransferase, on LUAD progression. mRNA expression was analyzed by quantitative PCR. Protein expression was tested by immunohistochemistry and immunoblotting. Cell proliferation was evaluated by MTT and EdU assays. Cell apoptosis was detected by flow cytometry and TUNEL staining. Transwell assays were used to examine cell invasion and migration. The influence of NSUN2 or the m5C reader YBX1 in CCT5 mRNA was analyzed by RNA immunoprecipitation assay and Actinomycin D treatment. In human LUAD, NSUN2 expression was upregulated, and high NSUN2 expression foreboded worse overall survival of LUAD patients. NSUN2 knockdown suppressed cell proliferation, diminished invasive and migratory potentials, and stimulated apoptosis in LUAD cells. NSUN2 was positively associated with CCT5 expression in LUAD and could mediate m5C modification of CCT5 mRNA. NSUN2 enhanced CCT5 mRNA stability and protein expression via two specific cysteines (C271 and C321). Moreover, YBX1 promoted CCT5 mRNA stability and protein expression. Additionally, restoration of CCT5 expression abolished NSUN2 deletion-mediated in vitro anti-proliferation, pro-apoptosis, anti-migration, and anti-invasiveness effects in LUAD cells, as well as in vivo anti-tumor growth behavior. Our study indicates that NSUN2 enhances the stability of CCT5 mRNA through a YBX1-m5C-dependent manner to drive LUAD progression. Targeting the NSUN2/CCT5 axis may be a potential approach to combat LUAD.</p> Graphical Abstract <p></p>