Oral squamous cell carcinoma (OSCC) is a common human malignant tumor with high mortality. So far, the molecular pathogenesis of OSCC remains largely unclear. Heterogeneous nuclear ribonucleoprotein (hnRNP) A1 is an important multi-function splicing factor and closely related to tumorigenesis. hnRNP A1 is overexpressed in various tumors, and promotes aerobic glycolysis and elongation of telomere, but the function of hnRNP A1 in cell cycle and proliferation remains unclear. We found that hnRNP A1 was overexpressed in OSCC tissues, and was required for the growth of OSCC cells. Moreover, hnRNP A1 was highly expressed in the G2/M cell cycle phase. Knockdown of hnRNP A1 induced G2/M arrest. DNA microarray assay result showed that hnRNP A1 regulated the expression of a number of target genes associated with G2/M phase. Moreover, hnRNP A1 controlled the alternative splicing of CDK2 exon 5. These findings suggested that hnRNP A1 plays key roles in the regulation of cell cycle progression and pathogenesis of OSCC.