Aim: The aim of this study was to compare and evaluate the efficacy of different diagnostic aids for diagnosis of dental caries and to compare the validity in terms of sensitivity and specificity of all four diagnostic modalities for diagnosis of caries. Materials and methods: Occlusal surfaces of 100 primary and permanent molars were examined using the four diagnostic systems (visual, intraoral camera, DIAGNOdent, and DIAGNOdent with dye). These results were compared with operative intervention gold standard. Sensitivity and specificity were calculated for each diagnostic system for both enamel and dentin caries. Interrater agreement was calculated for each diagnostic system using kappa statistics. Results: For both enamel and dentin caries, the highest sensitivity values were provided by DIAGNOdent (0.91 and 0.72) and lowest for visual examination on wet surface (0.60 and 0.50). For both enamel and dentin caries, the specificity was found to be highest for intraoral camera on dry surface and lowest for visual examination. The DIAGNOdent gave the highest value of interrater agreement (kappa), i.e., 0.816 as compared with 0.03 for visual examination. Conclusion: The study clearly demonstrated that DIAGNO-dent was the most accurate and valid system tested for the detection of occlusal caries. It has the advantage of quantifying the mineral content, helping to improve the diagnostic efficacy and treatment and accurate assessment of fissures where the visual examination alone is not adequate, thus complementing the traditional dental examination. How to cite this article: Zaidi I, Somani R, Jaidka S, Nishad M, Singh S, Tomar D. Evaluation of different Diagnostic Modalities for Diagnosis of Dental Caries: An in vivo Study. Int J Clin Pediatr Dent 2016;9(4):320-325.