Oral diseases not only greatly impact patients’ daily lives, but also pose a severe threat to their overall health. Due to the constant exposure of saliva to oral diseases, the former plays a vital role in their diagnosis and monitoring. Exosomes, nanosized bilayer lipid encapsulated nanovesicles, are widely present in saliva and can be released by any type of cell. Exosomes inherit features from their mother cells in both physiological and pathological conditions. The molecular characteristics and expression levels of exosomes depend on their cellular origin, and they can directly reflect the physiological state of the body and cells. This makes salivary exosomes a promising source for early detection and monitoring of oral diseases. As a result, researchers have been exploring the potential use of exosomes as biomarkers for diagnosing and predicting various oral diseases. This review provides an overview of the composition, separation and function of salivary exosomes. It also discusses their potential as diagnostic and prognostic markers for several oral diseases, including periodontitis, primary Sjögren’s syndrome, oral mucosal diseases, hand-foot-mouth disease and oral squamous cell carcinoma. By studying salivary exosomes, researchers hope to improve the early detection and monitoring of oral diseases, leading to better outcomes for patients.