Previous studies found that melanoma antigen genes (MAGE) were antigens expressed in various tumor cells but hardly expressed in normal tissues, and their unique expression pattern made them highly promising for cancer immunotherapy. MAGE-A10 was a member of the MAGE family, and although it was expressed in various tumors, its specific function remained unclear. In this study, we conducted a comprehensive pan-cancer analysis of MAGE-A10 expression, prognostic value, DNA methylation, genetic variation, function, immune infiltration, and drug sensitivity using multiple public databases. The results showed that MAGE-A10 was highly expressed in tumor tissues of most cancer types and was associated with poor prognosis. Additionally, MAGE-A10 was closely related to methylation levels, genetic variation, immune cell infiltration, immune therapy response, and chemotherapy resistance, possibly due to its role in regulating gene expression, cell differentiation, and immune response. Validation experiments in gastric cancer found that high expression of MAGE-A10 significantly affected patient prognosis. Gene set enrichment analysis (GSEA) indicated that high expression of MAGE-A10 was closely associated with the binding of histone deacetylases. Cell experiments showed that knocking down MAGE-A10 significantly reduced the proliferation, migration, and invasion capabilities of gastric cancer cells, which might be related to its regulation of the expression of cell adhesion molecule cadherins. In conclusion, this study indicated that MAGE-A10 was a potential tumor prognostic biomarker and immunotherapy target and played an important role in the proliferation, migration, and invasion of gastric cancer cells.