Toluidine blue is a valuable adjunctive diagnostic tool for identifying potentially malignant and malignant oral lesions. This metachromatic vital stain demonstrates reliable sensitivity for detecting dysplastic changes through selective binding to nucleic acids in epithelial tissues. Although the specificity varies across studies, toluidine blue significantly enhances the accuracy of clinical examinations in identifying high-risk lesions. Current evidence supports its application in biopsy site selection, surgical margin delineation, and screening. This review synthesizes recent findings on the diagnostic utility of toluidine blue and its potential future applications in oral medicine.