The use of synthetic insecticides has become widespread and useful for decades. However, due to not being eco- friendly and development of resistance in these organisms plants natural products essential oil components have shown significant potentials for insect control. Hence, laboratory bioassays were conducted to investigate bio-efficacy of Chenopodium ambrosioides L: (Chenopodiaceae) essential oil on adult Callosobruchus maculatus F. (Coleoptera: Bruchidae). On the basis of 24 hr and 48 hr median lethal toxicity (L50). Essential oil of C. ambrosioides was toxic on C. maculatus adults at 0.50 Mg/m2 and 0.20 Mg /m2 in 24 hr Lc50. Also 48 hr Lc99 values obtained show that essential oil of tested plant was 0.90 Mg/m2 and 0.18 Mg/ m2 toxic on adult C. maculatus. The study shows that essential oil of C. ambrosioides have potentials as fumigants for protecting cowpea from damage of C. maculatus