Exosomes are nanoscale extracellular vesicles containing a variety of bioactive substances that are widely involved in intercellular material transport and information transfer， and play an important role in a variety of pathophysiological processes. Mood disorders often result in difficulty in recognition， unclear diagnosis， and difficult treatment due to their clinical complexity. There are differences in the quantity and phenotype of exosomes between patients with mood disorders and healthy controls. This article reviews the relevant research on exosomes in patients with mood disorders， and explores the possibility of exosomes from different sources as biological diagnostic markers as well as therapeutic targets for mood disorders.