Hepatocellular carcinoma (HCC) has a pathogenesis that remains elusive with restricted therapeutic strategies and efficacy. This study aimed to investigate the role of SMG5, a crucial component in nonsense-mediated mRNA decay (NMD) that degrades mRNA containing a premature termination codon (PTC), in HCC pathogenesis and therapeutic resistance. We demonstrated an elevated expression of SMG5 in HCC and scrutinized its potential as a therapeutic target. Our findings revealed that SMG5 knockdown not only inhibited the migration, invasion, and proliferation of HCC cells but also influenced sorafenib resistance. Differential gene expression analysis between the control and SMG5 knockdown groups showed an upregulation of MAT1A in the latter. High expression of MAT1A, a catalyst for S-adenosylmethionine (SAM) production, as suggested by TCGA data, was indicative of a better prognosis for HCC. Further, an enzyme-linked immunosorbent assay showed a higher concentration of SAM in SMG5 knockdown cell supernatants. Furthermore, we found that exogenous SAM supplementation enhanced the sensitivity of HCC cells to sorafenib alongside changes in the expression of Bax and Bcl 2, apoptosis-related proteins. Our findings underscore the important role of SMG5 in HCC development and its involvement in sorafenib resistance, highlighting it as a potential target for HCC treatment.