Background: Nutrition plays a crucial role in children's growth and academic performance. However, Indonesia still faces nutritional issues among elementary school children, such as stunting, obesity, and low awareness of healthy lifestyles.Riskesdas 2018 and SKI 2023 data indicate a high prevalence of these issues, requiring further intervention. Nutrition education through visual media, such as illustrated storybooks, has been proven effective in enhancing children's understanding and behavior toward balanced nutrition. Objective : To determine the effectiveness of the illustrated storybook in improving knowledge and behavior regarding balanced nutrition among fifth-grade students elementary school. Methods: This study utilized a quasi-experimental design with a pretest-posttest comparison group design. It was conducted in Pajangan District, Bantul, Yogyakarta. A sample of 64 fifth-grade students was equally assigned to either the experimental or the control. Data were collected using a multiple-choice knowledge questionnaire and a Likert-scale attitude questionnaire. Data analysis involved paired sample t-test, Wilcoxon, independent sample t-test, and Mann-Whitney tests. Results: There were significant increases in the mean scores of both knowledge and attitudes regarding balanced nutrition from pretest to posttest 1 and posttest 2 within each group (p < 0.05). However, bivariate analysis revealed no significant differences in effectiveness between the illustrated storybook and the poster in improving students' knowledge (p > 0.05) or attitudes (p > 0.05). Conclusion: Both the illustrated storybook and the poster are equally effective and feasible tools for nutrition education to enhance knowledge and attitudes regarding balanced nutrition in elementary school students. Keywords : illustrated storybook, knowledge, attitude, balanced nutrition