Protein O-fucosyltransferase 1 (POFUT1) is the enzyme that adds O-fucose through O-glycosidic linkage to conserved serine or threonine residues in the epidermal growth factor-like repeats of a number of cellular surface and secreted proteins. Our previous study using microarray technology showed that significant upregulation of POFUT1 occurs in oral squamous cell carcinoma (OSCC)-derived cell lines compared to human normal oral keratinocytes. The aim of the present study was to examine the status of POFUT1 mRNA and protein expression in OSCC-derived cell lines and human primary OSCCs. POFUT1 mRNA was upregulated significantly (P<0.05 for both comparisons) in five OSCC-derived cell lines and primary OSCCs using quantitative reverse transcriptase-polymerase chain reaction. Immunohistochemistry data indicated that POFUT1 protein expression levels were consistent with mRNA expression status in OSCC-derived cell lines and primary OSCCs. Furthermore, POFUT1 expression status was correlated significantly (P=0.048) with the primary tumor size. The proliferation of POFUT1 knockdown cells was inhibited significantly compared with that of control cells. These results indicated that POFUT1 expression can contribute to cancer progression and that POFUT1 may serve as a diagnostic marker and a therapeutic target for OSCCs.