This study summarised the association between ultra-processed food (UPF) consumption and dental caries in children and adolescents through a systematic review and meta-analysis. The search of PubMed, Cochrane, Web of Science and Scopus databases using the ‘PECOS’ strategy retrieved 1462 eligible articles. Only studies with humans aged ≤ 19 years; that assessed groups of any UPF or specific UPF items; that measured dental caries as the decayed, filled and missing surfaces or teeth indexes, based on the WHO criteria; cross-sectional, case–control, cohort and all types of interventions that examined the adjusted association between UPF consumption and dental caries were included. All studies received qualitative evaluation. Meta-analysis using random-effects models combined multivariable-adjusted OR for case–control and cross-sectional studies and risk ratio (RR) for longitudinal studies of the highest v. lowest category of UPF consumption. Forty-two studies were included in the qualitative synthesis and twenty-seven in the meta-analysis. The pooled RR was 1·71 (95 % CI 1·31, 2·24), and the pooled OR was 1·55 (95 % CI 1·37, 1·75). The highest OR was found among participants who had dental caries prevalence >70 % (OR = 3·67, 95 % CI 2·16, 6·23). Better evidence quality was found among cohort studies that evaluated children <6 years old. The findings suggest that higher UPF consumption is associated with greater dental caries in children and adolescents. Public health efforts to reduce UPF consumption are needed to improve the oral health of children and adolescents.