Mosquitoes spread terrible diseases like chikungunya, yellow fever, malaria, dengue, Japan encephalitis and lymphatic filariasis in human beings even causes many deaths in every year. Chemical insecticides cause adverse effect in human beings, also to the environment. In this work, we sought a credible, eco friendly tool to control the vector mosquitoes at their larva stage. It reveals an eco-friendly and effective larvicidal activity of the Deoxyribonucleic acid (DNA) capped colloidal Silver nanoparticles. Characterizations of the Silver nanoparticles were done using absorption spectra and SEM. Spectra shows a predominant peak at 425nm and the SEM image shows the particles size is about 45nm. The third instars of Culex larvae were treated using these colloidal Silver nanoparticles, also the mortality rate for 24 hours was observed with 100% mortality rate at 10 ppm. The LC50, LC90 and confidence interval at 95% were investigated. Colour analysis and the SEM image of the treated larva were performed and confirm that the colloidal Silver nanoparticles were accumulated all over the skin surface of the larva which causes death.