Many arthropods (insects) have been associated with bacterial endosymbionts. These bacterial endosymbionts provide various advantages to insects, including nutritional, physiological, environmental, and evolutionary benefits. This is because of the various advantages of endosymbionts in their insect hosts. This has caused serious global issues leading to crop damage worldwide. This chapter describes the procedure of polymerase chain reaction (PCR) to detect such bacterial endosymbionts in insects.