Endophytes that live in plant tissues without causing any symptoms have become major sources of biologically active secondary metabolites that have important medicinal applications. These endophytic fungi and bacteria are capable of synthesizing a diverse range of compounds that are similar to their host plants’ metabolites. Major classes of secondary metabolites created by endophytes include alkaloids, phenolics, flavonoids, terpenoids, and polyketides. Such metabolites display a broad range of biological activities, comprising antimicrobial, anticancer, antioxidant, anti-inflammatory, antidiabetic, cardioprotective, and neuroprotective effects. Notable compounds such as Taxol, huperzine A, resveratrol, pestacin, and vincristine have been identified from various endophytic species and are being explored for their role in the treatment of cancer, neurological disorders, cardiovascular diseases, and microbial infections. The ability of endophytes to express silent biosynthetic gene clusters and adapt metabolite production in response to host or environmental cues further enhances their biotechnological value. Advances in co-culture strategies and epigenetic modulation have improved metabolite yields and enabled the discovery of novel compounds. As sustainable alternatives to plant harvesting, endophytes hold immense promise for drug discovery and development, offering a renewable and eco-friendly source of pharmacologically active molecules. Continued exploration of endophytic diversity at different geographical locations may unlock new pathways for therapeutic innovation.