Abstract: Early diagnosis and treatment of gastric cancer are important owing to its high morbidity and mortality rates. However, further research needs to be conducted in this field. We require more sensitive diagnostic techniques and more accurate treatment methods than those currently available to detect and treat gastric cancer effectively in its early stages. Secreted by cells, exosomes are vesicles that carry various small bioactive molecules, such as proteins, RNA, and DNA. Exosomes are a medium of intercellular communication, transmitting biological information and mediating the biological processes of recipient cells. In tumors, exosomes have key roles of transmitting information in the tumor microenvironment and regulating cellular immune responses. In recent years, advances have been made in the research of the mediatory involvement of exosomes in cancer, including in stomach cancer cells proliferation, invasion, recurrence, and metastasis, as well as treatment resistance. Thus, exosomes play a substantial role in the early detection and targeted therapy of gastric cancer. This article reviews the research progress of exosomes in the diagnosis and treatment of gastric cancer.