Purpose: To determine the incidence of caries in a 3-year follow-up of obese adolescents. Materials and Methods: Seven-hundred eighty five 13-year-old school children were selected randomly. Caries was recorded according to WHO criteria and body mass index was assessed in a medical evaluation. With appropriate sample weighting, relationships between caries and other variables were assessed using the chi-squared test, Kruskal-Wallis H-test, and multivariable logistic regression. Results: At baseline, 185 (24.2%) adolescents presented with caries, having mean DMFT and DMFS scores of 0.9 ± 2.0 and 2.4 ± 3.6, respectively. The accumulated incidence of caries during the 3-year period of study was 16.5%, with mean DMFT and DMFS increments of 0.8 ± 0.2 and 1.1 ± 3.3, respectively. Obese and overweight adolescents had a 3.7 times (95% CI = 1.3-6.8) greater chance of developing caries after adjusting for socioeconomic status, gender, use of fluoridated dentifrice, and past caries experience. Conclusion: Obese and overweight adolescents were at a higher risk of developing new caries in a 3-year-follow-up. Keywords: caries, incidence, obesity, overweight