Background: The present study reports the inhibitory effects of biogenic nanoparticles synthesized from Tridax procumbens stem (fresh and powder) aqueous extract on seed germination and seedling growth of Vigna radiata. These synthesized nanoparticles were well characterized by UV-visible spectroscopy; SEM; XRD and FTIR analysis. The constituents in the extract were also well characterized using FTIR analysis. The cytotoxic propertiesof the biogenic nanoparticles were then compared with the individual aqueous extract and vincristin (an anti-cancerous drug- used for ease in cancer.). The inhibition of seed germination and seedling growth was found to be dose-dependent and was suitable to quantify the bioactivity of biogenic nanoparticles preparations. Objective: The present investigation, emphasizes on simulating the activity of the synthesized biogenic nanoparticles from T. procumbens withan anticancerous drug __ampersandsignndash;vincristine using in vitro bioassay system (Kumar and Singhal, 2009). The growth promotion and/or retardation activity of crude plant extractis also described. Method:After reviewing number of peer-reviewed published articles the safest and eco-friendly method for the synthesis of the nanoparticles had been adopted. Biogenic nanoparticles were later well characterized by SEM, XRD, and FTIR analysis. Their activity against anticancerous drug __ampersandsignndash; vincristine, was tested using an in vitro bioassay on Vigna radiata. Results: Present study brings out the role of biogenic nanoparticles in inhibiting seed germination which was dose dependent. With vincristin comparable inhibition was observed. The plant extract, bionanoparticles and vincristin, promoted water imbibitions by the seeds though their higher concentrations inhibited this process. Reduction in water imbibitions, caused by these failed to trigger processes leading to reduced seed germination and radicle decay. The growth retardation following these treatments could be attributed to the inhibition of cell division and radicle protrusion brought about by osmotic stress (de Castro et al., 2000). From these observations it could be safely inferred that the plant extracts exhibited effective inhibitory activity, though biogenic nanoparticles and vincristin were most effective at 1.0 and 2.0 mg ml-1. Conclusion: Biogenic nanoparticles are eco-friendly, cost effective, and rapidly synthesized, and hence are more acceptable than the anti-cancerous drugs available in the market. The latter have side effects, cost issues, toxic chemicals involved in their synthesis, storage complexities, etc. The present study opens new avenue for medical sciences where plant extract synthesized nanoparticles via __ampersandsignldquo;green route__ampersandsignrdquo; can be the safer alternative than synthetic anti-cancerous products.