Purpose: To assess the oral health knowledge, attitude and practices of 15-year-old schoolchildren in Udupi Taluk, Southern India and to identify their social determinants. Materials and Methods: In this cross-sectional study, the sample was selected using stratified cluster random sampling. A self-administered questionnaire was filled out by the participants and evaluated using bivariate and multivariate analyses. Results: A total of 664 children were assessed. About 90% of participants had knowledge about causes of dental caries and the role of toothbrushing in its prevention. Lower proportions (40% to 60%) of participants were aware of gum disease and the role of fluoride and dental floss. A majority (>90%) of the children used a toothbrush and toothpaste, 63.3% of the children did not know whether their toothpaste contained fluoride or not, 61.9% of them cleaned their teeth two or more times a day and only 18.2% of the children visited the dentist for routine check-ups. In the multivariate analysis, a rural area of residence was associated with increased odds of inadequate oral hygiene behaviour (OR: 1.67, 95% CI: 1.10-2.52), of not having recently visited a dentist (OR: 1.89, 95% CI: 1.20-2.98) and of doing so only due to pain (OR: 2.52, 95% CI: 1.57-4.05). Attending private school was associated with decreased odds of these (OR: 0.36, 95% CI: 0.24-0.55; OR: 0.56, 95% CI: 0.36-0.89; OR: 0.39, 95% CI: 0.25-0.63 respectively), but it contributed significantly to a higher diet score (i.e. more sugary products consumed) (ß: 9.11. 95% CI: 2.97-15.25). Conclusion: There is a need to improve the oral health knowledge, attitude and practices in the target population with emphasis on improvement of oral hygiene and dental visit behaviours amongst rural and government school children and diet in private school children. Keywords: adolescent, health attitudes, health knowledge, health practice, India, socioeconomic factors