Culex quinquefasciatus (C. quinquefasciatus) is found in tropical and warm temperate regions and can transmit several viral diseases like Elephantiasis or Filariasis, West Nile fever, St. Louis encephalitis, and Japanese encephalitis causes millions of deaths every year. Long term use of synthetic pesticides to control mosquitoes, has led to the emergence of insecticide resistant vector, ecological imbalance, and harm to mammals, water contamination, toxicity to non-target organisms and residual effects. Therefore, plant based products are being searched and evaluated all over the world as an alternative control. The present study evaluated the efficacy of essential oil of Tagetes erecta (T. erecta) and Cymbopogon nardus (C. nardus) as a larvicidal, ovicidal, ovipositional deterrency and adulticidal agent against C. quinquefasciatus. Various bioassays against the IVth instar larvae, eggs and adults of C. quinquefasciatus were carried out. Five different concentrations of 10, 20, 40, 80,160, 320, 640 ppm was prepared for T. erecta whereas 20, 40, 80,160,320, 640, 1280 ppm concentrations were prepared for C. nardus essential oil to get LC50. Mortality data was calculated by Logprobit method of Finney using SPSS 16 (SPSS 2010) following Abbott method. The GCMS analysis of the essential oil of T. erecta and C. nardus was also conducted to estimate the presence of bioactive compunds in the essential oils. The essential oil of T. erecta and C.nardus, showed LC50 at 42.02 ppm and 160.29 ppm respectively after 24 hours. Whereas LC50 after 48 hrs is recorded at 39.25 ppm in T. erecta and 94.39 ppm in C. nardus against C. quinquefasciatus. At 40 ppm, T.erecta showed ovicidal activity with 40.99%, ovipositional activity with 57.80% and adulticidal activity with 88.00%. On the other hand, C. nardus at 160.29 ppm exhibited ovicidal activity with 77.63%, ovipositional activity with 73.33% and adulticidal activity with 73.6%. Many active phytochemicals was also found in the essential oil of T. erecta and C. nardus. It is concluded that the essential oil of both T. erecta and C. nardus are very effective mosquitocidal agent against C. quinquefasciatus. However T. erecta shows more effective results in comparision to C. nardus.