Storages pests presenting a major threat to storage commodities throughout the world from recent decades with causing severe economic losses to a variety of food products at large scale. Cypermethrin and phosphine are becomes major insecticides and fumigants as a grain’s protectants against Tribolium castaneum and Rhyzopertha Dominica. Unfortunately, due to repeated applications of these both control agents most of the major insect pests of storages developing resistance speedily. Under such circumstances current study was focused on to evaluate the resistance mechanism of field collected strains of these two major insects’ pests. Our results showed that both pests showed maximum resistance against cypermethrin, while in case of phosphine more mortality was observed which was indicated as less resistant to T. castenum and R. Dominica. Maximum mortality was observed (26.86±2.89) and (38.23±3.65) after 72 h of exposure of phosphine against T. castaneum and R. Dominica, cypermethrin showed minimum which was (25.41±2.73) and 926.60±3.28) respectively. The LC₅₀ value of both collected strains showed that phosphine was more resistant against T. castenum and R. Dominica while cypermethrin was detected less resistant. We hope this research could provide a greater-understandings for practical application of insecticides and fumigants for the control of storages pests.