Microbial insecticides are the exploitation of diseases causing organisms to reduce the population of insect pests below damaging levels. The microorganism?s that have been found suitable for microbial control are fungi, bacteria, viruses, protozoa and nematodes. Over 3000 micro organisms have been reported to cause diseases in insect, viruses, protozoa, and nematodes. Among these bacteria are the potential microbial control agents and among them, Bacillus thuringiensis proved to be the superior one against lepidopteran caterpillars. Entomopathogenic nematodes are microscopic round worms that attack and kill insect caterpillars/ grub and thy continue their life cycle by reproducing with in the dead host. Spores of the entomopathogenic fungus adhere to the insect skin and on germination penetrate the body wall eventually killing the insect. The most commonly used are Metarhizium anisoplea against coconut rhinocerous beetle, Fusarium palidosarum against cowpea aphid and Paecilomyces liliaceneus against white flies. Cautious application of microbial insecticides will provide good control of insect pests, chiefly available and eco-friendly in nature.