Exosomes, small bilayer vesicles secreted by all cells, are recognized as a novel communication tool among distant organs. They can cross the blood-brain barrier and be taken up by specific brain cells, altering the brain microenvironment and possibly playing a role in pathological conditions such as brain metastasis and neurodegenerative diseases. Intestinal bacteria also release small membrane vesicles called "bacterial extracellular vesicles" (BEVs), which can invade blood vessels and affect distant tissues in a manner similar to exosomes, suggesting that BEVs also play a role in disease progression in the brain-gut axis. Here, we will discuss the latest findings of the relationship between exosomes, including BEVs, and multiple brain pathologies.