Green synthesis of silver nanoparticles was successfully done using Cleome viscosa plant extract, simple, rapid, eco-friendly and a cheaper method. In this study, we used C. viscosa extract for synthesizing silver nanoparticles which reduces silver nitrate into silver ions. The obtained AgNPs were characterized by UV, FTIR, XRD, FESEM-EDAX and TEM analysis. They were also analyzed for their biological activities. The presence of biosynthesized AgNPs (410–430 nm) was confirmed by UV–visible spectroscopy and also crystal nature of AgNPs confirmed through XRD analysis; FT-IR spectrum was used to confirm the presence of different functional groups in the biomolecules which act as a capping agent for the nanoparticles. The morphology of AgNPs was analyzed using SEM and the presence of silver was confirmed through elemental analysis. The size of the nanoparticles was in the range of 20–50 nm determined by TEM. The green synthesized AgNPs exhibited a good antibacterial activity against both Gram negative and Gram positive bacteria. Furthermore, the green synthesized AgNPs showed reliable anticancer activity on the lung (A549) and ovarian (PA1) cancer cell lines.