This study examines the toxicological effects of silver (Ag), zinc oxide (ZnO) nanobiopesticides (NBPs) on Helicoverpa armigera larvae, a significant pest of various crops worldwide. The nanoparticles were synthesized using a green method. This study investigates the effects of silver (Ag), zinc oxide (ZnO), and synergistic silver-zinc oxide (Ag-ZnO) nanobiopesticides on the activities of antioxidant enzymes such as catalase (CAT), superoxide dismutase (SOD) and glutathione peroxidase (GPx) in the gut tissue of third instar larvae of Helicoverpa armigera. The larvae were fed on cotton leaves containing different concentrations of NBPs and enzyme activities were measured to evaluate oxidative stress responses. Results showed a dose-dependent increase in SOD, CAT and GPx activities across all NBPs treatments indicating oxidative stress caused by reactive oxygen species (ROS). The combined Ag-ZnO NBPs had the greatest effect on enzyme activity implying increased toxicity. These findings demonstrate the potential of NBPs as effective pest control agents by disrupting antioxidant defense mechanisms, offering insights into their application in integrated pest management strategies.