Aim This study was aimed at verifying the relationship between childhood obesity and dental caries. Method A total of 2 651 preschool children were examined for this cross-sectional study in Recife, Pernambuco, Brazil; 1 338 of them attended public schools and 1 313 private schools. The clinical data and anthropometric measurements were obtained in line with WHO criteria. Pearson chi-square and Mann-Whitney tests were used, with a 5 % margin of error. Results The prevalence of child obesity was 9 % (n=240). The highest prevalence was observed amongst children in private elementary schools (p<0.0001). The prevalence of dental caries was 19 % (n=504). The DMFT index was smaller in non-obese individuals (p=0.0267). The average value of dental caries, lost teeth and DMFT were significantly higher among children in public elementary schools than amongst those in private pre-schools (p<0.0001). Conclusion No relationship was found between dental caries and obesity. Suitable health policies should be adopted so as to minimise the high prevalence of dental caries among this population.