Objective: The main objective was to investigate the association of household food insecurity (HFI) with child oral health. A secondary objective was to explore potential dietary and non-dietary mediators of the HFI-child oral health relationship.Design: Cross-sectional data from the nationally representative Ecuadorian National Health and Nutrition Survey (2018) were analysed. The data included self-reported child oral health, HFI (Food Insecurity Experience Scale), diet (FFQ) and oral care behaviours (toothbrushing frequency, toothpaste use). The association of HFI with the reported number of oral health problems was examined with stereotype logistic regression. Parallel mediation analysis was used to explore potential dietary (highly fermentable carbohydrate foods, plain water) and non-dietary (toothbrushing) mediators of the HFI-oral health relationship. Bias-corrected standard errors and 95 % CI were obtained using non-parametric bootstrapping (10 000 repetitions). Effect size was measured by percent mediation (PM).Setting: Ecuador.Participants: 5-17-year-old children (n 23 261).Results: HFI affected 23 % of child households. 38·5 % of children have at least one oral health problem. HFI was associated with a greater number of oral health problems: 1-2 problems (adjusted odds ratio (AOR) = 1·37; 95 % CI (1·15, 1·58); P = 0·0001), 3-4 problems (AOR = 2·21; 95 % CI (1·98, 2·44); P = 0·0001), 5-6 problems (AOR = 2·57; 95 % CI (2·27, 2·88); P = 0·0001). The HFI-oral health relationship was partially mediated by highly fermentable carbohydrate foods (PM = 4·3 %), plain water (PM = 1·8 %) and toothbrushing frequency (PM = 3·3 %).Conclusions: HFI was associated with poorer child oral health. The HFI-oral health relationship was partially mediated by dietary and non-dietary factors. Longitudinal studies are needed to replicate our findings and investigate the role of other potential mediators. [ABSTRACT FROM AUTHOR]