NIN1/RPN12 binding protein 1 homolog (NOB1) facilitates the maturation of the 20S proteasome and is then degraded by 26S proteasome to complete 26S proteasome biogenesis. It also accompanies the pre-40S ribosomes during nuclear export and is cleaved at D-site of 20S pre-rRNA to form mature 18S rRNA in growing cells. NOB1 was reported to be involved in the development of several types of cancer. However, the role of NOB1 in oral squamous cell carcinoma (OSCC) has not been addressed. In the present study, the expression of NOB1 in 50 OSCC patients with different genders, ages, TNM and pathological grades was detected using immunohistochemistry and western blotting. A loss-of‑function study was carried out by the lentivirus‑mediated siRNA knockdown of NOB1 in the CAL27 and TCA-8113 OSCC cell lines. The results showed that, NOB1 expression increased with pathological grades. In the CAL27 and TCA-8113 cell lines, knockdown of NOB1 in OSCC cells decreased cell proliferation, colony formation, increased cell apoptosis and also induced cell cycle arrest in the S phase. The results suggested that NOB1 is important in OSCC development and serves as a candidate indicator of aggressiveness and a therapeutic target of OSCC.