To enhance the global food supply and address human demand, it is crucial to improve crop production and sustainability. The growth of the human population and various human activities pose threats to food security. While traditional agricultural systems have long relied on agrochemical inputs to increase crop yields, these practices harm the environment. Therefore, there is a current emphasis on exploring soil-derived biological resources and plant microbes to develop environmentally friendly agricultural methods. The microbiota of the rhizosphere and endosphere are influenced by biotic and abiotic factors, respectively, to some extent. Plant microbes and their hosts have a mutually dependent relationship. Endophytic fungi (EF) are fascinating fungal species associated with hosts, as they can penetrate both intercellular and intracellular domains of host tissues and provide benefits to their hosts. Endophytic fungi employ various strategies to regulate phytopathogens, including inducing and enhancing plant resistance. This improves plants’ ability to withstand stress through gene regulation, synthesis of fungal metabolites, and production of hormone signaling molecules. Exploring the potential of beneficial endophytes as bioinoculants for biological fertilizers and their integration into plant breeding and disease management programs appears to be a promising alternative to agricultural chemicals. Beneficial endophytic fungal organisms have the ability to enhance plant health by limiting the growth of pathogenic fungi. This disease-prevention method depends on endophytic fungus and host plants coexisting. Understanding beneficial endophytic fungal species along with their interactions with pathogens and host plants, as well as making judgements about them, is a significant challenge associated with endophyte biocontrol techniques. The investigation of the antibiosis activity of fungal endophytes can be conducted through the development of biocontrol agents, contributing to the integrated management of plant diseases. Research on endophytic fungi as bioinoculants is growing. The biological defense mechanism of fungal endophytes against plant diseases is the primary focus of this chapter. It also discusses the problems and major obstacles that still require investigation.