Currently, nanotechnology (NT) and nanoparticles (NPs) have gained significant attention in the scientific field due to their diverse application history. Particularly, in environmental applications, their antibacterial efficiency in fisheries due to antibacterial resistance. However, the NPs have been found toxic in the environment. Therefore, the current study aimed to fabricate less toxic NPs using environmentally dried leaves to check their antibacterial efficacy and possible toxicity against grass carp. The findings confirmed the good dispersity of obtained AgNPs, which further showed promising antibacterial activity against several bacterial isolates including Staphylococcus with a zone of inhibition (23.73 ± 0.57 nm). Also, the AgNPs were exposed to the grass carp (Ctenopharyngodon idella) for possible toxicity and toxic effects. First, the bioaccumulation of AgNPs was significantly observed in gills followed by intestines and muscles (p < 0.05). Finally, the AgNPs mainly accumulate in the liver, followed by the intestine, gills, and muscles. Additionally, the deposition of AgNPs in various organs resulted in histological alteration such as necrosis and infiltration of red blood cells in the intestine and the fusion of gill lamella. Hence, the synthesized NPs using dried leaf extract could be a promising approach in applied science. The significant features of the nanoparticles in the present work using green synthesis can help in synthesizing less toxic materials.