Salivary diagnostics is emerging as a propitious tool with a multitude of clinical applications. It has been into practice for centuries but has recently garnered scientific researchers and clinicians' interest due to its added benefits. In this review, we have emphasized the various components of saliva and its functionalities, an introduction to salivary diagnostics, and its application in the detection and prognosis of many ailments all around the globe. A segment about saliva's special uses in animals and its role in therapeutics and forensics has also been focused. With the continually evolving technologies and chemical equipment, several devices have been devised which are used in salivary diagnostics. The utilization of saliva and its biomarkers as a non-invasive diagnostic agent in several diseases, including malignancies, caries, novel coronavirus, psychological stress, diabetes, and much more, has been discussed.