Entomopathogenic fungi (EPF) are the pathogenic microorganisms that attack and kill insects and other arthropods. Despite being a significant part of the ecosystem, various insect species pose a threat to economically important crops, leading to substantial agricultural losses annually. As a result, sustainable pest management has drawn significant attention over the years, and biocontrol agents play a major role in contributing to it. Application of EPF as biocontrol agents provides an effective and ecofriendly alternative to harmful pesticides and insecticides. The intricate interplay between EPF and insects is marked by a constant coevolutionary arms race occurring over thousands of years. In this consistent tug-of-war, the insect hosts utilize a diverse range of defense mechanisms and immune responses. This chapter underscores the various types of immune responses by the host, such as behavioral, physical, cellular, and humoral responses, further highlighting the various strategies employed by EPF as a countermeasure against each kind of immunity, ensuring efficient and successful host invasion. Additionally, this chapter explores the different stages of fungal infection, shedding light on the mechanisms behind pathogen invasion and the dual role of miRNA in insect immunity and how it acts as both an asset and a liability. Insights into this interplay between host and pathogen help us gain a deeper understanding of the coevolutionary arms race and can help enhance pest management strategies via genetic engineering. Consequently, the biocontrol potential of EPF can be enhanced in different aspects by overcoming the limitations and improving the overall virulence and pathogenicity, thereby ensuring efficient pest management.