Objectives Obesity and dental caries have become increasingly prevalent challenges to public health. Research results into the relationship between obesity and dental caries in children have been mixed and inconclusive. The aim of this review and meta-analysis was to provide evidence to quantify the relationship between obesity and dental caries in children using a systematic approach. Methods A systematic search for papers between 1980 and 2010 addressing childhood obesity and dental caries was conducted and a random effects model meta-analysis applied. Results Fourteen papers met the selection criteria. Overall, a significant relationship between childhood obesity and dental caries (effect size = 0.104, P = 0.049) was found. When analysed by dentition type (primary versus permanent), there was a nonsignificant association of obesity and dental caries in permanent and primary dentitions, yet on accounting only for standardized definitions for assessment of child obesity using body mass index, a strong significant relationship was evident in children with permanent dentitions. Moderating for study country of origin (newly ‘industrialized’ versus industrialized) showed a significant relationship between obesity and dental caries in children from industrialized but not newly industrialized countries. Cofactors such as age and socioeconomic class were significant moderators. Conclusions Future analysis should investigate these confounding variables, helping shape the future of obesity management programmes and oral health interventions, through determining common risk factors.