The insecticidal properties of essential oils prepared using water distillation method from aerial parts of Mentha piperita, Mentha pulegium, Zataria multiflora and Thymus daenensis were investigated on adult of Bruchus lentis and Callosobruchus maculatus. Essential oils were used in five concentrations and five replications. Mortality rate of insects were recorded after 3, 6, 24, 48 and 72 hours. Results indicated that the longer exposure of insect to essential oil and the higher concentration of essential oil, increased mortality of the two species in all treatments. There was significant difference among mortality effect of the essential oils. The LC50 value of M. piperita after 24 hours for B. lentis and C. maculatus was 14.62 and 13.70 μl/l air respectively, while the values of LC50 were 92.32 and 95.80 for M. pulegium, 58.43 and 99.94 for Z. multiflora and 63.97 and 65.55 μl/l air for T. daenensis, respectively. The least LT50 recorded was in T. daenensis essential oil with 26.21 and 24.15 hours against B. lentis and C. maculatus, respectively.