Malnutrition remains a major public health issue in developing and transitional countries and food insecurity is a major indicator of the nutritional status in these societies. This research aimed to investigate the status of household food insecurity and sociodemographic factors affecting it among 2–6 years old children in an urban area in the southeast of Iran. A community-based survey was conducted from September to January 2018 on 421 children aged 2–6 years who were selected using stratified cluster random sampling. They lived in six different areas in an urban area in the southeast of Iran. Data was collected using the U.S. Department of Agriculture Food Security questionnaire and anthropometric measurements. Our study showed that the prevalence of food insecurity among children was 81.7% consisting of 2.6% with low food security, 9.2% with moderate food insecurity, and 69.9% with very low food security. The weight gain of those children who were in the low food security group, was 2.63 times lower than those children in the food security group. Moreover, the chance of weight gain in the low food security and in the moderate food insecurity groups was less as 1.91 and 1.41 times, respectively. Food insecurity in children aged 2–6 years is influenced by various sociodemographic factors including weight and height, mother’s education level, sanitation as access to water closet (WC). Policymakers should plan to improve the quality of life and health of the children through improving their food security.