Random amplified polymorphic DNA analysis by polymerase chain reaction (RAPD-PCR) was used as a tool to screen genetic variation in Tribolium castaneum adults treated by LC50 of Bacillus thuringienisis, Beauveria bassiana, teflubenzuron and spinetoram using ten random oligonucleotide primers for amplification. The results of cluster analysis using Dice coefficient among treated and untreated T. castaneum adults revealed that adult beetles were grouped into 2 main clusters. One contains control adults. The other cluster was divided into 2 main subclusters; one includes adults treated with LC50 of B. thuringienisis and teflubenzuron while the other subcluster contains adult beetles treated with LC50 of B. bassiana and spinetoram. Furthermore, the transcriptional response of Cytochrome P450 gene to each of the used insecticides in T. castaneum was examined by qRT-PCR. The results revealed that CYP450 was up-regulated by all the four insecticides tested. The highest level of up-regulation was recorded in adult beetles treated with LC50 of teflubenzuron (25.9-fold) followed by B. thuringienisis treated adults (7.6- fold), and spinetoram (6.8-fold). The least level of up-regulation was recorded in adults exposed to LC50 of B. bassiana (2.9- fold) as compared to control group.