Culex quinquefasciatus is also known for being a potential vector for all arboviruses diseases like Filariasis, Japanese Encephalitis, West Nile virus etc. The main purpose of this current study is to observe the larvicidal activity of synthesized silver nanoparticles from the leaves extracts of Thuja occidentalis against the C. quinquefasciatus. The leaves extracts of Thuja reduce the silver nitrates into silver nanoparticles. The synthesized silver nanoparticles were taken at different doses such as 90ppm, 100ppm, 200ppm and 300ppm as well as fed to the 3rd or 4th instars larvae of C. quinquefasciatus. The mortality rates were recorded at different time intervals such as 3hrs, 6hrs, 12hrs, 24hrs, 48hrs and 72hrs. The 100% mortality rates were recorded after 72hrs in each synthesized silver nanoparticles doses against the C. quinquefasciatus. T. occidentalis leaves extracts can yield the silver nanoparticles and the synthesized silver nanoparticles has the good larvicidal activity against the C. quinquefasciatus.