The following plant extracts were used as reducing and stabilizing agents in green synthesis of silver nanoparticles (AgNPs): Ardisia argentea, Aegiceras corniculatum, Polycarpaea corymbosa, Maesa perlaria, and Schima wallichii. As the reducing power and total phenolic content in the extracts increased, the absorbance of surface plasmon resonance (SPR) of the resulting AgNPs also increased. The characteristic SPR of AgNPs was clearly observed at 400∼500 nm. The resulting AgNPs showed spherical-shapes, which was revealed by field emission transmission electron microscopy images. An average size was obtained between 10.4±0.3 nm and 22.2±0.8 nm. The cytotoxicity of AgNPs was investigated in A549 and HeLa cells. There was a dose-dependent manner of cytotoxicity in both cells. Interestingly, at the highest dose, AgNPs synthesized with A. corniculatum extract exhibited the highest cytotoxicity and induced high levels of reactive oxygen species (ROS). In addtion, higher levels of ROS was produced by smaller AgNPs. In cell cycle analysis, cell death was observed in the treatment with AgNPs which was occurred by G2/M phase arrest. The results obtained herein support the potential of plant-mediated green synthesis of AgNPs as a promising anticancer nanomedicine.