Dendrimers are highly branched, synthetic polymers with well-defined structures, making them promising candidates for drug delivery and therapeutic applications. This review summarizes the in vivo applications of dendrimers in drug delivery, gene therapy, and diagnostics. Dendrimers can be synthesized using divergent or convergent methods, allowing for precise control over their size, shape, and surface properties. Their unique structure enables efficient cellular uptake through mechanisms such as clathrin-mediated endocytosis, caveolin-mediated endocytosis, and macropinocytosis. Dendrimers can be functionalized with various ligands to target specific cells or tissues, enhancing their therapeutic potential. In cancer therapy, dendrimers have been used to deliver chemotherapeutic agents, such as doxorubicin, and to target tumors with high efficiency. Studies have shown that dendrimer-based systems can improve drug delivery, reduce toxicity, and enhance therapeutic outcomes. In neurodegenerative diseases, dendrimers have been explored for their ability to deliver gene therapy agents, such as siRNA or plasmid DNA, to the central nervous system. In infectious diseases, dendrimers have demonstrated antiviral and antibacterial properties, particularly when functionalized with specific ligands or charged groups. Dendrimers also show promise in diagnostics, where they can be used as contrast agents for imaging techniques such as MRI and CT. Their ability to enhance the accumulation of imaging agents in tumor lesions and to target specific proteins makes them valuable tools for early disease detection. Additionally, dendrimers can act as drugs themselves, offering new treatment options for various conditions. Despite their potential, challenges remain in the clinical translation of dendrimer-based therapies, including issues related to long-term toxicity, biocompatibility, and the need for standardized evaluation methods. However, ongoing research and development suggest that dendrimers could play a significant role in the future of nanomedicine, particularly in drug delivery systems and targeted therapies. The continuous advancement of nanotechnology is expected to lead to the development of more sophisticated and effective dendrimer-based nanocarriers, further expanding their applications in pharmaceutical and medical fields.Dendrimers are highly branched, synthetic polymers with well-defined structures, making them promising candidates for drug delivery and therapeutic applications. This review summarizes the in vivo applications of dendrimers in drug delivery, gene therapy, and diagnostics. Dendrimers can be synthesized using divergent or convergent methods, allowing for precise control over their size, shape, and surface properties. Their unique structure enables efficient cellular uptake through mechanisms such as clathrin-mediated endocytosis, caveolin-mediated endocytosis, and macropinocytosis. Dendrimers can be functionalized with various ligands to target specific cells or tissues, enhancing their therapeutic potential. In cancer therapy, dendrimers have been used to deliver chemotherapeutic agents, such as doxorubicin, and to target tumors with high efficiency. Studies have shown that dendrimer-based systems can improve drug delivery, reduce toxicity, and enhance therapeutic outcomes. In neurodegenerative diseases, dendrimers have been explored for their ability to deliver gene therapy agents, such as siRNA or plasmid DNA, to the central nervous system. In infectious diseases, dendrimers have demonstrated antiviral and antibacterial properties, particularly when functionalized with specific ligands or charged groups. Dendrimers also show promise in diagnostics, where they can be used as contrast agents for imaging techniques such as MRI and CT. Their ability to enhance the accumulation of imaging agents in tumor lesions and to target specific proteins makes them valuable tools for early disease detection. Additionally, dendrimers can act as drugs themselves, offering new treatment options for various conditions. Despite their potential, challenges remain in the clinical translation of dendrimer-based therapies, including issues related to long-term toxicity, biocompatibility, and the need for standardized evaluation methods. However, ongoing research and development suggest that dendrimers could play a significant role in the future of nanomedicine, particularly in drug delivery systems and targeted therapies. The continuous advancement of nanotechnology is expected to lead to the development of more sophisticated and effective dendrimer-based nanocarriers, further expanding their applications in pharmaceutical and medical fields.