Objective: To examine the prevalence of household food insecurity and compare dietary intake by food security status in a representative Korean population. Design: Cross-sectional. Food security status of households was classified using an eighteen-item food security questionnaire. The nutrition survey comprised questions on dietary habits, a 24 h dietary recall and a semi-quantitative FFQ. Setting: The 2012 Korea National Health and Nutrition Examination Survey. Subjects: A total of 3007 households completed the food security questionnaire. Family members within each household aged ≥1 year (n 7118) participated in the nutrition survey. Results: Results from the 2012 survey indicated that 88·7 % of Korean households showed food security. The remaining 11·3 % (9·3 % for food insecurity without hunger and 2·0 % for food insecurity with hunger) were in food-insecure households. The prevalence of household food insecurity was 13·2 % in households with children and 10·3 % in households without children. Mean daily intakes of energy, fat and carbohydrates were not significantly different between food-secure and food-insecure adults. In contrast, mean daily intakes of protein, crude fibre, vitamins and minerals as well as weekly consumption frequencies of vegetables, seaweeds, fruits, fruit juice, nuts, and milk and milk products were significantly lower in food-insecure adults compared with food-secure adults. Conclusions: The study demonstrated that food insecurity is associated with reduced intakes of healthy foods and nutrients essential for health and growth in a representative Korean population.