BIRC5 is an immune-related gene that inhibits apoptosis and promotes cell proliferation. It is highly expressed in most tumors and leads to poor prognosis in cancer patients. This study aimed to analyze the relationship between the expression level of BIRC5 in different tumors and patient prognosis, clinical parameters, and its role in tumor immunity. Genes co-expressed with BIRC5 were analyzed, and functional enrichment analysis was performed. The relationship between BIRC5 expression and the immune and stromal scores of tumors in pan-cancer patients and the infiltration level of 22 tumor-infiltrating lymphocytes (TILs) was analyzed. The correlation of BIRC5 with immune checkpoints was conducted. Functional enrichment analysis showed that genes co-expressed with BIRC5 were significantly associated with the mitotic cell cycle, APC/C-mediated degradation of cell cycle proteins, mitotic metaphase, and anaphase pathways. Besides, the high expression of BIRC5 was significantly correlated with the expression levels of various DNA methyltransferases, indicating that BIRC5 regulates DNA methylation. We also found that BIRC5 was significantly correlated with multiple immune cells infiltrates in a variety of tumors. This study lays the foundation for future research on how BIRC5 modulates tumor immune cells, which may lead to the development of more effective targeted tumor immunotherapies.