Among the registered and marketed insecticides, 10 different insecticides belonging to 8 chemical classes (Acrinathrin 5.7% SC, Acetamiprid 5% SL, Dinotefuran 10% SL, Spinetoram 5% WG), Abamectin 1.8% EC, Emamectin benzoate 2.15% EC, Chlorfenapyr 5% EC, Cyclaniliprole 4.5% EC, Fluxametamide 9% EC, and Flometoquin 10% SC) were investigated for insecticide resistance in western flower thrip (Frankliniella occidentalis) strains collected from 3 regions (Andong, Bonghwa and Youngyang) of Gyeonsangbuk-do area. The insecticidal activity was significantly different depending on the origin of the F. occidentalis strain tested. The most effective insecticides included; flometoquin against the Andong strain, and spinetoram against both Andong and Bonghwa strains. These two insecticides showed high efficacy of more than 90% when compared with their recommended doses. Additionally, Flometoquin also showed a high efficacy of 81.3% against the Youngyang strain. The LC50 and RR50 of flometoquin against the Youngyang strain was 55.676ppm and 0.54, respectively. The LC50 of spinetoram was lowest in the Bonghwa strain (0.683ppm), with a resistance ratio (RR50) of 0.07. When tested against the Andong strain, spinetoram was also highly effective with a LC50 and RR50 value of 1.014ppm, and 0.1, respectively. Notably, fluxametamide was highly effective (100% efficacy) against the lab strain. Among the 10 insecticides used in this study, F. occidentalis strain from Andong showed resistance to 6 insecticides (Acrinathrin, Acetamiprid, Dinotefuran, Abamectin, Chlorfenapyr, Cyclaniliprole); the strain from Bonghwa was resistant to 7 insecticides (Acrinathrin, Acetamiprid, Dinotefuran, Abamectin, Emamectin benzoate, Chlorfenapyr, Cyclaniliprole); and the Youngyang strain exhibited resistance to 8 insecticides (Acrinathrin, Acetamiprid, Dinotefuran, Spinetoram, Abamectin, Emamectin benzoate, Chlorfenapyr, Cyclaniliprole). No insecticide resistance was expressed in studies involving flometoquin and fluxametamide against all the tested F. occidentalis strains in Gyeongsangbuk-do area. In conclusion, in order to avoid continued development of insecticide resistance in F. occidentalis, it is necessary to pay close attention to the choice of the available insecticides in Gyeongsangbuk-do area. Flometoquin and fluxametamide are still effective against all strains, and can therefore be recommended for use in control of F. occidentalis in Gyeonsangbuk-do.