Nanotechnology is a trend that highly advanced over the past thirty years, addressing and resolving more challenges across different fields. In this investigation, biogenic silver nanoparticles (Ag-NPs) were formed using Brevibacillus agri as an endophytic bacterial strain and utilized as a safe approach to control the spread of medical insect, Culex pipens. The formed Ag-NPs were characterized by UV-vis analysis that showed maximum surface plasmon resonance at a wavenumber of 420 nm. Fourier transforms infrared analysis exhibits the role of various biomolecules in bacterial filtrate reduction and capping as-formed NPs. The sizes of biogenic NPs were 20 – 50 nm with spherical shapes with weight and atomic percentages of Ag ions of 46.20% and 13.96% respectively as shown by SEM-EDX analysis. The crystalline structure was confirmed by XRD. The mortality of various instar larvae and pupae of C. pipens were concentration-dependent and showed maximum percentages of 88.4±0.95, 76.3±0.8, 69.6±1.1, 52.1±1.4, and 47.3±1.01% for first to fourth instar larvae and pupae respectively at a concentration of 30 ppm. The concentrations of proteins, carbohydrates, and lipids of III instar larvae were decreased from (172.1 ± 4.31, 118.1±4.6, and 463.1±1.32 µg/g) for the control to (54.2±1.72, 91.3±2.17, 204.6±9.31 µg/g) respectively upon treatment with 30 ppm of Ag-NPs.