Purpose: To study the dental caries experience among adolescent school children in Chennai city using the ICDAS-II scoring system. The secondary objective was to identify associated risk factors to different thresholds of dental caries defined by ICDAS. Material and Methods: Two hundred and thirty-seven children (13–17 years) from five schools across Chennai city were included using simple random sampling. After obtaining assent to participate in the study and satisfying the selection criteria, 200 children were screened for dental caries using ICDAS-II. The population was assessed for the following risk factors: sociodemographic status, habits, diet, plaque and salivary parameters. Prevalence of dental caries was estimated at the following thresholds: normal (ICDAS-0/1), mild caries (ICDAS-2), moderate caries (ICDAS-3/4) and extensive caries (ICDAS-5/6). Backward logistic regression analysis was performed to identify risk factors at different thresholds and crude odds ratio was calculated for statistically significant risk factors. Results: The overall prevalence of dental caries (ICDAS 3–6) was 57.5% (95% CI 48–62%). The proportions of children at different caries thresholds were: ICDAS-2 – 55% (95% CI:48–62%), ICDAS-3/4 – 51% (95% CI:44–58%) and ICDAS-5/6 – 25% (95% CI:19–31%). Reduced pH was statistically significant for moderate and extensive caries (OR 6.24, 95% CI 1.18–32.78 and 1.73, 95% CI 1.18–1.92, respectively) and the quantity of saliva was statistically significant for mild and moderate caries (OR 4.48, 95% CI 2.94–8.23 and 3.97, 95% CI 2.65–7.03, respectively). Low buffering capacity was associated with mild caries OR 5.71, 95% CI 2.82–18.2). Interobserver correlation was 0.91. A non-statistically significant value using Hosmer–Lemeshow Goodness of Fit test indicated that all three models predict the true estimate of the population. Conclusion: The proportions of children with mild and moderate caries were high considering their age group. The risk factors associated with mild caries were different from those associated with moderate and extensive caries. Keywords: adolescent children, dental caries, dental plaque, ICDAS, risk assessment, saliva