Currently, little is known about the mechanism(s) of AgNP-induced toxicity. Many previous studies, however, have provided strong evidence for a link between the AgNP-mediated production of ROS and the subsequent generation of oxidative stress. In the current study, the effects of Ag nanoparticles on the MCF-7 breast cell line were examined, and the biomarkers related to stress oxidative including GSH, superoxide dismutase, catalase, and ROS generation were evaluated. The results showed that Ag nanoparticles induced intracellular ROS generation in a dose- and time-dependent manner. Therefore, various studies should be performed to investigate the toxic effects of this substance on different cells.