OBJECTIVE: Children from food-insecure families (ie, families that lack access to sufficient, safe, and nutritious food) are at risk for developmental problems. Food insecurity disproportionately occurs among low-socioeconomic status (SES) and low-income families; however, interventions that supplement families' income or diet have not eradicated food insecurity. This may be because food insecurity is also related to nonfinancial factors such as the presence of maternal mental health problems. To clarify whether addressing mothers' mental health problems may be a promising strategy for reducing the burden of food insecurity, we tested the hypothesis that low-SES families are especially vulnerable to food insecurity when the mother experiences depression, alcohol or drug abuse, psychosis spectrum disorder, or domestic violence. METHODS: We used data from a nationally representative cohort of 1116 British families (the Environmental Risk Longitudinal Study). Food insecurity, family SES, maternal mental health and exposure to domestic violence, and children's behavioral outcomes were measured by using validated methods. RESULTS: Overall, 9.7% of study families were food-insecure. Among low-SES families, controlling for income variation, food insecurity co-occurred with maternal depression (odds ratio [OR]: 2.82 [95% confidence interval (CI): 1.62-4.93]), psychosis spectrum disorder (OR: 4.01 [95% CI: 2.03-7.94]), and domestic violence (OR: 2.36 [95% CI: 1.18-4.73]). In addition, food insecurity predicted elevated rates of children's behavior problems. CONCLUSIONS: Among families with young children, food insecurity is frequent, particularly when the mother experiences mental health problems. This suggests that interventions that improve women's mental health may also contribute to decreasing the burden of food insecurity and its impact on the next generation.