Membrane-associated ring-CH-type finger 8 (MARCH8) belongs to the MARCH family of membrane-bound E3 ubiquitin ligases. The N-terminus of MARCH family members contains the C4HC3 RING-finger domain, which can bind to E2 ubiquitin-conjugating enzymes, ubiquitinate substrate proteins, and thereby promote protein degradation through the proteasome pathway. The aim of this study was to determine the role of MARCH8 in hepatocellular carcinoma (HCC). We first analyzed the clinical relevance of MARCH8 based on The Cancer Genome Atlas database. Immunohistochemical staining was used to detect MARCH8 expression in human HCC samples. Migration and invasion assays were conducted in vitro. Cell apoptosis and cell cycle distribution were analyzed by flow cytometry. The expression of phosphatase and tensin homolog deleted on chromosome 10 (PTEN)-related markers was evaluated in HCC cells through Western blot analysis. MARCH8 was highly expressed in human HCC tissues, and its high expression was inversely correlated with patients' survival. Disrupting MARCH8 expression significantly inhibited the proliferation, migration, and cell cycle progression of HCC cells, while also promoting their apoptosis. In contrast, the overexpression of MARCH8 significantly enhanced cell proliferation. Mechanistically, our results showed that MARCH8 interacted with PTEN and suppressed the protein stability of PTEN by enhancing its ubiquitination level via the proteasome. MARCH8 also activated AKT in HCC cells and tumors. In vivo, overexpression of MARCH8 could promote the growth of hepatic tumors through the AKT pathway. MARCH8 may promote the malignant progression of HCC by promoting the ubiquitination of PTEN, thereby relieving the inhibitory effect of PTEN on the malignant phenotype of HCC cells.© 2023 The Authors. Molecular Carcinogenesis published by Wiley Periodicals LLC.