One of the most important diagnostic and therapeutic tools in the field of nanomedicine is the silver nanoparticle. The significant anticancer herb Ctenolepis garcinii ethanolic extract was used in the current study to optimize a cost-effective production technique for silver nanoparticles. We looked at AgNPs ability to fight cancer and their probable role in apoptosis. The crystal sizes of the stable, spherical, biosynthesized AgNPs range from 20 to 51 nm. Breast cancer MDA-MB-231 cells exhibit concentration-dependent growth suppression in the MTT cell viability assay (IC50, 9.5 µg/mL). Additionally, the fluorescence microscopic analysis demonstrates that AgNPs activate caspases 3 and 9, which result in nuclear condensation (DAPI assay) and morphological alterations (AO/EB assay) in the cell membrane, both of which ultimately result in apoptotic cell death (Annexin V/PI test). Additionally, it was shown that AgNPs cause MDA-MB-231 cells to produce reactive oxygen species (ROS) and mitochondrial membrane potential, which regulate oxidative stress. This is the first study to describe the creation of a silver nanoparticle by the action of a Ctenolepis garcinii extract and an analysis of the cellular and molecular mechanisms underlying apoptosis.