To minimize exposure to contagions such as seasonal influenza and COVID-19, we need noninvasive sampling and diagnostic methods, such as human saliva. Saliva is gaining attention as a suitable diagnostic medium because of its applicability in a field setting. Compared to blood, the collection, transport, and storage of saliva samples are easy, noninvasive, cost-effective and cause little discomfort for patients. Evidence shows that salivary biomarkers can be used to detect and monitor a plethora of oral and systemic conditions, including cancer. Human saliva contains many biomolecules, such as proteins, RNA, and DNA. In this chapter, we highlight the potential clinical utility of saliva as a liquid biopsy and explore recent discoveries in the applications of salivary biomarkers in cancer research. In addition, we reviewed the current state of salivary diagnostics and its associated technologies, and its potential as the preferred medium of cancer diagnosis, monitoring, and prognosis and future aspirations.