PLU-1/JARID1B (jumonji AT rich interactive domain 1B) is one of the testis cancer antigens and functions as a histone demethylase in the regulation of various human types of cancers. However, its functions in head and neck squamous cell carcinoma (HNSCC) are rarely reported. The aim of the present study was to examine PLU-1/JARID1B expression levels in HNSCCs and to investigate its role in cancer cell proliferation. In the present study, we found that PLU-1/JARID1B mRNA was upregulated in all tested HNSCC cell lines. Immunohistochemical staining showed that PLU-1/JARID1B protein expression was detected in 87.8% (87/99) of the HNSCC cases. A positive association was observed between high PLU-1/JARID1B expression and higher Ki-67 labeling in the HNSCC samples (Pearson r=0.6514, P=0.0003). Stable PLU-1/JARID1B knockdown by PLU-1-shRNAs in the HNSCC cell lines suppressed cell growth both in the in vitro and in vivo studies. Moreover, PLU-1/JARID1B knockdown resulted in G1 arrest and early apoptosis by suppressing Bcl-2 family members in the HNSCCs. These data indicate that PLU-1/JARID1B is overexpressed in HNSCCs and is associated with tumor proliferation and apoptosis. Therefore, PLU-1/JARID1B represents a candidate proliferation biomarker for HNSCC diagnosis and treatment.