In this article, light induced plant extract mediated one pot synthesis of silver nanoparticles (AgNPs) has been demonstrated and potential mechanistic insight in the synthesis has been investigated. Bioactive molecules containing medicinal plant Cassytha filiformis has been explored for the synthesis of silver nanoparticles. The as-synthesized silver nanoparticles were characterized by various analytical techniques including Ultraviolet-visible spectroscopy (UV-Vis), High Resolution Transmission Electron Microscopy (HR-TEM), Dynamic Light Scattering (DLS) and Fourier Transform Infrared Spectroscopy (FT-IR). Among different light sources (sunlight, room light, UV) applied the sunlight was found to be efficient external stimuli to induce rapid synthesis of AgNPs at room temperature. Modified DPPH assay indicated that polyphenolic compounds were most likely involved in the synthesis of AgNPs. Possible molecule responsible for the synthesis of AgNPs was identified, purified and characterized. Potential biomedical applications such as antibacterial, antifungal and anticancer activities of AgNPs have been evaluated. Irrespective of nature of pathogenic strains nanoparticles exhibited significant antibacterial activities against Gram positive (Streptococcus aureus) and Gram negative (Escherichia coli) bacterial pathogens. It showed higher activity on E. coli than on S. aureus. Distinct antifungal activity (MIC=5.244μg/ml) and remarkable anticancer activity (IC50=10μg/ml) was found against Candida albicans and HCT116 (colorectal carcinoma) cells, respectively. Taken together, these findings suggested that light induced plant generated silver nanoparticles could be used for various biomedical purposes.