South Korea and North Korea share the same environment on the Korean peninsula, but they differ in socio-economic conditions, which leads to differences in crop productivity and status of food security. This study aimed at assessing food security in South Korea and North Korea by analyzing food demand and supply from 1991 to 2020. Food security was assessed by determining whether the food supply met the demand in two countries. South Korea achieved food security due to decreasing consumption, diverse nutrition, and stable rice productivity despite a reduction in cultivated paddy areas. In contrast, North Korea has faced food insecurity for 30 years, caused by a growing population, a lack of dietary diversity, and low crop productivity. To overcome food shortage, the North Korean government needs to focus on improving agricultural productivity through comprehensive reforms of agricultural infrastructures, rather than simply expanding low-productive cultivated areas. Although this study was conducted with limited data for North Korea, it sought to collect and utilize open and publicly accessible data. In the long term, both South Korea and North Korea should prepare for the impacts of climate change, considering agriculture-related sectors such as water and energy.