objective: We explored the IgG1 heavy chain constant region (IGHG1) roles in tongue squamous cell carcinoma (TSCC) progression, as well as to probe the underlying mechanisms. methods: The expression patterns of IGHG1 in TSCC tissues and cell lines were tested by Western blotting, quantitative real-time PCR (RT-PCR) and immunohistochemistry (IHC) technologies. The relationship between IGHG1 expression level and the overall survival and clinicopathologic features of patients with TSCC were evaluated to assess the clinical value of IGHG1. The effects of IGHG1 on cell function were determined by Cell-Counting Kit-8 (CCK-8), clone formation, flow cytometry and in vivo tumor formation assays. results: The expression of IGHG1 in TSCC tissues and cell lines was significantly elevated at both mRNA and protein levels. IGHG1 expression levels closely related to T classification (p=0.008), clinical stage (p=0.011), and node metastasis (p=0.005) in TSCC patients. Upregulation of IGHG1 with lentivirus infection significantly increased Janus kinase 1 (JAK1) expression and the phosphorylation level of signal transducer and activator of transcription 5 (STAT5). In addition, IGHG1 overexpression markedly enhanced cell proliferation, clone formation and tumorigenesis and inhibited cell apoptosis, whereas these effects were abolished when JAK1 was downregulated in SCC15 and SCC4 TSCC cell lines. conclusions: Collectively, this study reveals that IGHG1 functions as an oncogene in TSCC via activating JAK1/STAT5 signaling.