Abstract: The S100 calcium-binding protein family member A16 (S100A16) exhibits differential expression in various malignant tumors and plays a critical role in tumor progression, including effects on tumor cell proliferation, apoptosis, adhesion, epithelial-mesenchymal transition, migration, and invasion. Its aberrant expression is associated with adverse clinical outcomes, making it a potential prognostic biomarker. Furthermore, S100A16 is closely linked to the infiltration of immune cells within the tumor microenvironment, contributing to the establishment of an immunosuppressive state. The expression level of S100A16 in tumor-associated endothelial cells may also correlate with the formation of an inhibitory immune microenvironment. Additionally, S100A16 has been implicated in tumor chemotherapy resistance. This review summarizes recent advances in our understanding of the mechanisms by which S100A16 contributes to different types of tumors, its regulatory effects on the tumor immune microenvironment, and its role in drug treatment resistance. The aim of this review is to elucidate the underlying mechanisms of tumor prevention and treatment and provide a theoretical foundation for overcoming drug resistance in cancer therapy.