In the study, we investigated the cell viability, colony formation, mitochondrial membrane potential (ΔΨm), and expression level of cell cycle-related proteins (namely, cyclin A, P21, and CDK2) and apoptosis-related proteins (namely, Caspase-3, Bax, and Bcl-2) with the lung cancer cell line A549, 95D, and the subcutaneous xenograft models to explore the underlying mechanisms and molecular signaling pathways by which Biochanin A blocks the cell cycle and induces apoptosis. The gene discussed is CDK2; the disease is lung cancer.