B-cell lymphoma 2 (Bcl-2) is a founding member of the Bcl-2 family of regulatory proteins that can modulate cell apoptosis by inducing apoptosis (pro-apoptotic) or inhibiting apoptosis (anti-apoptotic). Bcl-2 is well-established as an important anti-apoptotic protein and is classified as an oncogene. It regulates mitochondrial dynamics and is involved in the regulation of mitochondrial fusion and fission. Additionally, in pancreatic beta cells, Bcl-2 and Bcl-XL are involved in controlling metabolic activity and insulin secretion. Genetic damage to the Bcl-2 gene can lead to various cancers, including melanoma, breast cancer, prostate cancer, chronic lymphocytic leukemia, and lung cancer. It may also be associated with schizophrenia and autoimmune diseases. Bcl-2 is also implicated in resistance to cancer treatment.