With the development of the biogenic nanotechnologies, scientists are looking new ways to design novel strategies for the treatment and diagnosis of cancer. Advances in nanotechnology have attracted many researchers to the biogenic synthesis of metallic NPs because of its advantages like, simple, fast, one pot processes, economical and biocompatibility. Medicinal plants are selected to be the best reservoirs of diverse phytochemicals for the biogenic synthesis of silver nanoparticles (AgNPs). In this review, the top point discussed is mechanistic advances in the synthesis of AgNPs from medicinal plant extracts. We have discussed the recent improvements achieved in the use of biogenic AgNPs as cancer theranostic agents. Anticipating all of the challenges in the field of cancer, we hope that biogenic AgNPs may become a potential cancer therapeutic and diagnostic agent in the near future.