In view of the recently increased interest in developing plant origin insecticides as an alternative to chemical insecticide, this study was undertaken to assess the larvicidal potential of the essential oil Cymbopogon flexeous (lemongrass) and Tagetes erecta (marigold) against medically important mosquito vector, Aedes aegypti. Essential oil was hydro distilled in the laboratory from the plants obtained from the CAP. Bioefficacy of the essential oil was evaluated under laboratory conditions using III instar mosquito larvae. The LC50 values of Cymbopogon flexeous are 136.8, 52.736 and 24.056ppm after 12, 24 and 48 h of exposure respectively. The LC50 values of Tagetes erecta are 81.765, 48.951 and 17.729ppm after 12, 24 and 48 hours of exposure respectively. Chi-square values were significant at p