This study aimed to compare the contents and illustrations of elementary and middle school science textbooks in Mongolia and Korea with the theme of 'Energy and Climate Change' and to study their status and trends. This study focused on 'change in the state of matter' among the energy components because energy contains many components. The research method is performed in these steps: after comparing and analyzing the contents and illustrations on 'changes in the state of matter' described in the currently used Mongolian and Korean elementary and middle school science textbooks, the contents and illustrations on 'climate change' were compared and analyzed. Elementary and middle school textbooks in both countries had sufficient contents on 'changes in the state of matter'; however, content on climate change is lacking and energy and climate change almost had no integrated content. Because of the study, the contents related to 'change of state of matter' in the science textbooks of both countries were similar, but the Korean textbook had more illustrations, exploration, and applications. While the Korean elementary school science textbook had four science stories about climate change, the Mongolian elementary school textbook had only one content. Middle school science textbooks contained relatively little content related to climate change and only included greenhouse gas-related content; therefore, they did not cover much content. Through our research, we would like to make the following suggestions: First, there is a need to consider adding content related to 'climate change' to Mongolian elementary school textbooks. Additionally, it appears that content related to 'climate change' in Korean textbooks should be organized as important content related to the achievement process, not as part of science stories, and should be linked to exploration. Second, science classes should place more emphasis on the usefulness and importance of content than on content and illustrations. Lastly, there is a need to include content related to 'climate change' rather than 'weather' or 'climate' in elementary and middle school textbooks in both countries as scientific and social content appropriate for the age of students.