In this study, Synergistic effect of gamma radiation in combination with Carum copticum C. B. Clarke essential oil as a safe and proper method to control of Trogoderma granarium Everts larvae was investigated. Experiments were designed at three different steps included: 1- Application of gamma radiation and essential oil at the same time. 2- Irradiation of Insects followed by essential oil. 3- Fumigation of insect by essential oil followed by gamma irradiation. Treatments are included different doses of 700, 800, 900 and 1000 Gy of gamma radiation and 5-100 microliter per liter of C. copticum essential oil was used. In order to calculate the values of LC1, LC5 and LC25, SPSS software was applied. The study was shown that combination of gamma radiation with C. copticum essential oil increased larvae mortality compared with the control, so that, the combination of 900 and 1000 Gy with doses of essential oil (14.25, 20.88 and 35.97 μl / l) increased the mortality to 100 % after 18 and 22 days while these gamma doses alone can be control only 20 % of larvae at the same time. It was concluded that maximum synergism occurred when 700 Gy of gamma radiation was applied with 14.25 μl / l of essential oil which in the mortality of larvae increased to 93±6.88 % after 35 days. The best interaction was obtained when fumigated larvae were exposed to irradiation. The results have shown that irradiation and essential oils can be used as success control of stored product pests.