Aim: This study aims to evaluate the impact of a novel multicomponent nutrition education program (United for Healthier Kids; U4HK) on the diet consumed during school lunch among preschool children. Methods: The program comprised four tools: hero plates, hero content, hero menus, and hero books and stickers. The program was implemented for 16 weeks. Food consumption and the quality of the menus were examined pre- and post-intervention. Results: The lunch nutrient profiling scores for fat and vitamin C improved from moderate (9.95) to good (10.87) and moderate (9.50) to very good (13.83), respectively. Vegetable and fruit consumption also increased significantly by 127.2% (6.0 (3.2, 12.9) grams to 13.7 (6.7, 18.9) grams, p<0.001) and 44.8% (8.1 (3.9, 12.4) grams to 11.7 (5.4, 21.8) grams, p<0.001), respectively. Compared to those in the Thai school lunch guidelines, the percentages of vegetable and fruit consumed increased by 16.0% (12.1% (6.4, 25.9) to 28.1% (13.4, 43.4)) and 8.8% (14.0% (6.8, 28.3) to 22.8% (8.5, 33.4)), respectively. Energy, carbohydrate, and fat intake increased significantly by 13.2% (179.1 (137.9, 220.8) to 202.7 (163.0, 243.2) kcal), 18.9% (18.1 (14.3, 21.7) to 21.6 (17.2, 25.6) grams), and 23.2% (6.7 (4.9, 9.9) to 8.2 (6.7, 10.2) grams), respectively. Conclusions: The U4HK program adopted all aspects that foster healthy eating, including a healthy environment, an attractive role model and increased repeatability of the exposure to healthy foods.