We investigated the association of household food insecurity (HFI) with developmental delays in 36–59-month-old preschool children (n 7005) using cross-sectional data from the 2018 Ecuadorian National Health and Nutrition Survey. HFI was assessed with the Food Insecurity Experience Scale and developmental delays with the Early Childhood Development Index. Log-binomial regression models estimated the association of HFI with global (overall) developmental delay (GDD) and delays in four individual developmental domains, adjusting for covariates. Nearly half of the children lived in households with marginal (24⋅5 %) or moderate-severe HFI (21⋅7 %). Eighteen percent were identified with GDD. Delays in the individual domains of literacy-numeracy, social-emotional, physical and cognitive development were identified for 64, 21⋅5, 3⋅3 and 3⋅1 %, respectively. GDD was more likely among preschool children from households with marginal (aPR = 1⋅29; 95 % C.I. = 1⋅10, 1⋅49) and moderate-severe HFI (aPR = 1⋅30; 95 % C.I. = 1⋅11, 1⋅51). Social-emotional development delays were also more likely among those from households with marginal (aPR = 1⋅36; 95 % C.I. = 1⋅19, 1⋅56) and moderate-severe HFI (aPR = 1⋅33; 95 % C.I. = 1⋅15, 1⋅54) different from the other three domains. Several other potentially modifiable risk (violent discipline, maternal depressive symptoms) and protective factors (adequate child stimulation, higher maternal education, handwashing with soap/detergent) were also independently associated with GDD and/or literacy-numeracy and cognitive delays. Our findings suggest that HFI is an independent risk factor for GDD and social-emotional developmental delays in Ecuadorian preschoolers. They underscore the importance of strengthening and expanding poverty reduction, food security and early childhood development policies and interventions to improve the opportunities for children to achieve their full developmental potential.