Biosynthesis of silver nanoparticles was achieved by novel simple green chemistry procedure using Achyranthes aspera leaf extract as a reducing and a capping agent. The present study focuses on larvicidal activity of synthesized silver nanoparticles (AgNPs) against Culex quinquefasciatus, Aedes aegypti and Anopheles stephensi. Range of concentrations of synthesized AgNPs (2, 4, 6, 8 and 10 mg/ml) and the aqueous extract (100, 50, 25, 12.5 and 6.25 mg/ml) were tested against the fourth instar larvae for 24 h exposure. The maximum efficacy was observed in the synthesized AgNPs against Cx. quinquefasciatus (LC₅₀ 2.48; LC₉₀ 8.14 mg/ml) and Ae. aegypti (LC50 3.68; LC90 8.92 mg/ml) whereas aqueous extract found to be effective against Cx. quinquefasciatus at a higher concentration. The synthesized AgNPs from A. aspera were highly potent than aqueous extract against all the three tested vectors. The synthesized AgNPs were characterized by UV-visible spectrophotometer, SEM, TEM, FTIR and XRD. This revealed a peak at 452 nm in leaf extract of A. aspera, indicating the production of AgNPs. The synthesized AgNPs were clearly distinguishable with the respective nanometers and the XRD spectrum confirmed the presence of silver ion and it was compared with the standard spectrum peaks. The FTIR spectra of AgNPs exhibited prominent peaks of organic molecules.