The present investigation aimed at assessing the diagnostic accuracy of DIAGNOdent compared to the International Caries Detection and Assessment System-II (ICDAS-II) in the detection of facial, smooth surface noncavitated carious lesions. Sixty patients were enrolled in the current study according to the eligibility criteria. There were 161 teeth with noncavitated, white spot carious lesions and 32 sound teeth. Before examination, teeth were cleaned and polished and all patients were assessed under standardized operating conditions: preset dental unit position, operating light, and prolonged air drying (approximately 5 s). All teeth were assessed by two calibrated examiners individually without any contact using ICDAS-II and DIAGNOdent. The diagnostic accuracy of DIAGNOdent device was determined, including sensitivity, specificity, overall accuracy, positive and negative predictive values, and receiver operating characteristic curve analysis. Chi-square test was conducted to compare the distribution of ICDAS-II and DIAGNOdent scores. Inter-observer agreement between assessors was evaluated using Cohen's kappa test. In the current study, DIAGNOdent had an overall accuracy of 84.45% with sensitivity and specificity of 87.58% and 96.87%, respectively, and +PV and -PV of 97.7% and 83.9%, respectively, when score 0 represented sound tooth surface, while scores 1 and 2 were considered clinically noncavitated carious lesions. Moreover, when only ICDAS score 1 was considered representing first visual change in enamel, DIAGNOdent had an accuracy of 74.15% with sensitivity and specificity of 83.53% and 90.62%, respectively, and +PV and -PV of 93% and 78.6%, respectively. In the present study, when only ICDAS score 2 was considered representing distinct visual change in enamel, DIAGNOdent had an accuracy of 100% with sensitivity and specificity of 100% and 100%, respectively, and +PV and -PV of 100% and 100%, respectively. The overall performance of DIAGNOdent was equivalent to the visual inspection using ICDAS-II. DIAGNOdent might be considered a useful adjunctive device for detection and monitoring development of noncavitated carious lesions on facial smooth surfaces.