Endophytes are commonly known as microorganisms, mainly bacteria and fungi, which live inside plant tissues without inducing symptoms. Considering the long-lived trees, endophytes have a fundamental role in preparing their hosts to face extreme weather conditions, drought, heat, cold, and pathogen and herbivore attacks. The current knowledge clearly demonstrates the importance of endophytes in shaping the plant diversity in a forest. Endophytes have an important capacity for biocontrol of forest diseases. Considering endophyte diversity and the range of various compounds and enzymes they can produce, endophytes can be used for various biotechnological applications.