AIM: This review provides a systematic evaluation of 94 stem cell clinical trials to treat neurodegenerative diseases, including Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis, and Huntington's disease. METHODS: Data were collected from using relevant search terms, focusing exclusively on stem cell therapy. Of the 8000+ participants in these trials, nearly 70% were enrolled in AD-related studies. Only three Phase 3 studies were conducted, and most trials were in the early phases (Phases 1 and 2). Mesenchymal stem cells, neural stem cells, induced pluripotent stem cells, and embryonic stem cells are used the most to treat neurodegenerative diseases. This review also explores the emerging fields of preclinical and clinical investigations of stem cell-derived exosome-based therapies for neurodegenerative diseases. RESULTS: Exosomes can cross the blood-brain barrier to deliver therapeutic molecules directly to the brain, offering a less invasive alternative to stem cell transplantation. Mesenchymal stem cell-derived exosomes, in particular, have demonstrated significant potential in preclinical models by reducing neuroinflammation, oxidative stress, and promoting neuronal regeneration. Additionally, recent advances in exosome engineering, including surface modifications, therapeutic agent loading, and transgenic modifications, have improved targeting, stability, blood-brain barrier delivery, and neural cell interactions, enabling targeted and effective treatment. Exosome-based therapies are in the preliminary phases of clinical investigation, with only three clinical trials. CONCLUSION: Given the increasing interest in exosome therapy, clinical investigations are expected to increase. This growth will be driven by ongoing advancements in exosome technology, a deeper understanding of their therapeutic potential, and escalating demand for innovative treatment strategies for neurodegenerative diseases.