Proliferation and metastasis are the core malignant characteristics in esophageal squamous cell carcinoma (ESCC) that contribute to poor prognosis. However, the mechanisms underlying cell proliferation and metastasis remain elusive. We explored the function of high-mobility group box (HMGB3) in promoting ESCC progression. HMGB3 expression in ESCC tissues and cell lines was quantified using quantitative PCR, Western blotting, and immunohistochemistry. The proliferative and migratory characteristics of ESCC cells were assessed using in vitro and in vivo assays, respectively. An RNA sequencing analysis was conducted to identify the downstream signaling pathways of HMGB3. Co-immunoprecipitation was performed to identify HMGB3-interacting proteins. HMGB3 transcriptional regulation was investigated using luciferase reporter and chromatin immunoprecipitation assays. Elevated levels of HMGB3 were observed in both patient-derived ESCC tissues and ESCC cell lines and were correlated with poor patient prognosis. HMGB3 up-regulation promoted ESCC proliferation and metastasis, whereas HMGB3 down-regulation inhibited these processes. Mechanistically, homeodomain protein transforming growth factor beta (TGF-β)-induced factor homeobox 2 (TGIF2) transcriptionally up-regulates HMGB3. HMGB3 subsequently activates TGF-β signaling through its regulation of and interaction with toll-like receptor 3 (TLR3), ultimately promoting ESCC proliferation and metastasis. Clinically, HMGB3 expression was positively correlated with TGIF2 and TGF-β, and patients with ESCC who positively co-expressed TGIF2/HMGB3, HMGB3/TGF-β, or TGIF2/TGF-β exhibited poor prognosis. The functional role of HMGB3 in ESCC proliferation and metastasis was illustrated in our research. Targeting the TGIF2/HMGB3/TLR3/TGF-β axis has the potential to serve as a promising therapeutic approach.