Use of chemical pesticides to combat pest infestations, has raised a number of issues, such as increasing concern for human health and environmental hazards. Chemical application in addition to environmental hazards may cause various diseases in consumers due to the transfer of the remaining poison to their bodies. Use of essential oils of aromatic plants as natural and safe insecticides as well as gamma irradiation have been introduced as environmental friendly methods without any toxic residue to control insect pests. Indian meath moal plodia interpunctella H. is one of the most important pests in different parts of the world, in particular the regions of Asia, Africa, Europe and the America. In the present study, various gamma-ray doses and the toxicity of the Thymus vulgaris L. as well as the effect of combining these two methods on biological processes of Indian meal moth plodia interpuctella H. is studied. The mortality rate of the egg stage and the last larvae was 100% respectively for 400 and 600 Gy and the percentage of adult emergence from the puppae stage was zero from 750 Gy. The results of the combination of pure essential oil and gamma ray showed the synergistic effect of these two factors when applied at doses of 15 μl /l essential oils and 25 Gy 25 and 21 μl /l essential oils and 25 Gy irradiation which caused 41.67% and 55.00% mortality of pest larvae respectively. Also, the application of 15 μl /l essential oils and 60 Gy and 25 μl /l essential oils and 60 Gy irradiation caused 33.33% and 43.33% mortality respectively in pupae.