The BAZ2B gene belongs to the bromodomain gene family. The proteins encoded by members of this gene family are important components of chromatin remodelling complexes and have a potential role in transcriptional activation. However, the biological significance of BAZ2B in pan-cancer is unknown. In this study, we comprehensively analysed the functional characteristics of BAZ2B in human cancers and its role in immune response using The Cancer Genome Atlas (TCGA), Gene Expression Album (GEO), Genotype-Tissue Expression (GTEx) databases, and tools such as TIMER 2.0 and cBioPortal, and found that BAZ2B is down-regulated in certain cancers, and its overexpression is associated with patients’ poor prognosis, such as bladder, breast and endometrial cancers. In addition, we demonstrated for the first time that BAZ2B was under-expressed in breast cancer cells and promoted proliferation, migration and apoptosis of breast cancer cells.