Neurodegenerative diseases (NDs) represent a growing public health burden characterized by progressive neuronal dysfunction, synaptic loss, and cognitive or motor decline. Despite extensive research efforts, current diagnostic and therapeutic strategies remain largely symptomatic and fail to address the underlying causes or halt disease progression. Extracellular vesicles (EVs), a heterogeneous population of lipid bilayer-enclosed particles released by virtually all cell types, have emerged as key mediators of intercellular communication in both health and disease. Their ability to carry proteins, lipids, and nucleic acids across biological barriers, particularly the blood–brain barrier (BBB), positions EVs as powerful candidates for novel diagnostic, therapeutic, and regenerative approaches in NDs. This chapter provides a comprehensive overview of the roles of EVs in neurodegenerative disease pathology and treatment. It begins with an introduction to EV classification, molecular cargo, and isolation techniques then examines their involvement in key disease mechanisms such as protein aggregation, neuroinflammation, and synaptic dysfunction. The chapter also explores the therapeutic applications of native and engineered EVs in preclinical models, along with current clinical efforts and regulatory considerations. Through this lens, EVs are positioned not only as biomarkers and drug delivery vehicles but also as biologically active agents capable of transforming how neurodegenerative diseases are diagnosed, managed, and potentially reversed.