Abstract: To investigate the impact and underlying mechanism of NOP2/Sun RNA methyltransferase 2 (NSUN2) on gastric cancer progression, TCGA database was used and revealed a significant upregulation of NSUN2 expression in gastric cancer tissues. Western blot analysis revealed that NSUN2 was upregulated in gastric cancer cells compared with gastric mucosal epithelial cells. Colony formation assays demonstrated an enhanced colony-forming capacity in NSUN2-overexpressing cells. Furthermore, Transwell assays showed a marked increase in cell migration and invasion upon high NSUN2 expression. Moreover, TCGA database analysis suggested ARMC9 as a potential downstream target of NSUN2. Subsequently, MeRIP-qPCR analysis revealed that NSUN2 overexpression could increase m⁵C modification of ARMC9 mRNA, and reduce its degradation rate, thus enhancing protein expression. Additionally, ARMC9 overexpression augmented cellular colony formation and migratory and invasive capabilities. These findings indicate that NSUN2 promotes gastric cancer progression by elevating m⁵C modification of ARMC9 mRNA, increasing its stability and enhancing its expression, therefore, NSUN2 and ARMC9 may serve as potential therapeutic targets for gastric cancer.