This study investigates the prevalence and key risk factors of household food insecurity in the climate-vulnerable coastal regions of Bangladesh. Primary data were collected through a cross-sectional survey in three coastal districts, providing comprehensive insights into sociodemographic and economic determinants of food insecurity in this underexplored region. The study included mothers of the children aged 6–59 months from 471 households and selected using a three-stage cluster sampling procedure. Household food insecurity was measured using the Household Food Insecurity Access Scale (HFIAS), and multivariable logistic regression was performed to identify the risk factors of food insecurity. The prevalence of household food insecurity was 28.7%, and a lower chance of experiencing food insecurity was found in households with younger heads (≤ 40 years) [AOR: 0.42; 95% confidence interval (CI): 0.20–0.90] compared to the older group. A lower risk of food insecurity prevalence was observed in households having educated mothers (AOR: 0.22; 95% CI: 0.08–0.58) compared to the noneducated group, higher monthly income (AOR: 0.09; 95% CI: 0.04–0.21) compared to lower income, and households located in the central (AOR: 0.21; 95% CI: 0.10–0.44) and western parts (AOR: 0.15; 95% CI: 0.06–0.34) compared to the eastern coastal region of the country. Household heads engaged in fishing and having mothers with chronic health issues were identified as significant predictors of food insecurity. Our study identified several sociodemographic and economic factors as significant predictors of food insecurity and suggested that effective interventions, including the enhancement of educational opportunities, promotion of income-generating activities, and support for the fisher community and those with chronic health conditions, are necessary to reduce household food insecurity in this region.