The activity of silver nanoparticles synthesized using aqueous extracts from leaves of Peganum harmala, Capparis sinaica and Salvia multicaulis against Culex pipiens third larval instar was tested. Biosynthesized silver nanoparticles (AgNPs) were characterized by Transmission Electron Microscope studies (TEM) and Ultraviolet-Visible (UV/VIS) spectroscopy. The TEM images revealed that the major population of the silver nanoparticles is found within the 10 to 22 nm range. Ultraviolet-Visible (UV/VIS) spectrophotometer analysis for synthesized AgNPs showed peaks between λ_max: 407-410 corresponding to the plasmon absorbance of the AgNPs. Results of larvicidal activity showed that, biosynthesized AgNPs have a great larvicidal activity against C. pipiens larvae at different concentrations ranging from 8.0 to 55.0 ppm, depending on plant extract used in synthesization and concentration of AgNPs. Complete larval mortality percent (100.0%) was recorded by AgNPs synthesized using aqueous extracts from leaves of P. harmala,Ca. sinaica and S. multicaulis at 20.0, 40.0 and 55.0 ppm, respectively. Based on LC₅₀ and LC₉₀ values, P. harmala-synthesized AgNPs was more effective against 3^rd instar larvae of C. pipiens than those of Ca. sinaica and S. multicaulis.