Exosomes represent a subtype of extracellular nanovesicles that are generated from the luminal budding of limiting endosomal membranes and subsequent exocytosis. They encapsulate or associate with obsolete molecules to eliminate or to transfer their cargos in intercellular communication. The exosomes are also released and transported between neurons and glia in the nervous system, having a broad impact on nerve development, activation and regeneration. Accumulating evidence suggests that the exosomes are attributed to the pathogenesis of several neurodegenerative diseases such as prion disease, Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis, as well as aging, in which the exosomes lack the capacity for cellular self-repair and spread their enclosed pathological agents among neurons. In this article, we review the current proposed functions of exosomes in physiological and pathological processes in the nervous system.