AgNPs synthesized from Menyanthes trifoliata for the control of malaria vector, An. stephensi. Synthesized nanoparticles were analyzed by UV-Vis spectrophotometry, SEM, XRD, FTIR, and EDAX. The nanoparticles were evaluated for their toxicity of larvae, pupae, insect growth regulatory activity and persistent study. The characterization studies confirmed that AgNPs are of size 10-50nm and spherical in shape. The concentrations ranging from 5-25 µg/mL tested against L1 to L4 larvae and pupae of An. stephensi. LC50 = 8.17, 9.78, 12.96, 16.73 and 20.11 µg/mL; LC90 = 19.57, 24.25, 29.64, 36.95 and 41.81 µg/mL treated all larval instars and pupae, respectively. The mortality rates were positively correlated with the concentration. Significant (P<0.05) changes in larval mortality were also recorded between the period of exposure of all larval instars. The larval and pupal growth was significantly diminished (IGR activity) by the action of AgNPs and its emergence inhibition EI50 and EI90 values are 1.87 (10.58) significantly noted. This study reported that toxic nature of AgNPs had a significantly higher impact on the third instar than others and their toxic effect lasted up to a 12-week period. These findings reported M. trifoliata synthesized AgNPs are novel, rapid, eco-friendly for mosquito control.