The identification of potential oncogenes plays an important role in finding novel therapeutic targets for many cancers, including hepatocellular carcinoma (HCC), which is one of the most common cancers worldwide. In our previous research, using microarray technology, we found that FAM83D was overexpressed in HCCs. However, whether the overexpression of FAM83D contributes to hepatocarcinogenesis remains unclear. In this study, we found that FAM83D was significantly upregulated in 76.6% (167 of 218) of the HCC specimens at the mRNA level and in 69.44% (50 of 72) of the HCC specimens at the protein level compared with adjacent non-cancerous liver specimens, as indicated by RT-PCR and immunohistochemical staining, respectively. The FAM83DmRNA expression level was positively correlated with the level of alpha-fetoprotein (AFP) (≥100 ng/ml), the clinical TNM stage, the presence of a portal vein tumor thrombus (PVTT), disease-free survival (DFS) and the overall survival (OS) time of the HCC patients (P < 0.05). Knocking down FAM83D significantly promoted the growth of Huh7 and HepG2 cells, as demonstrated in an RNA interference assay. Moreover, the DNA methylation status of the FAM83D promoter was significantly reduced in the HCC specimens with overexpression of FAM83D gene. Our data suggest that the upregulation of FAM83D, a potential oncotarget gene, may be triggered by epigenetic events and can contribute to hepatocarcinogenesis.