Undernutrition among school-age children remains to be highly prevalent in developing countries. The adverse impact of undernourishment among school-age children could significantly affect their cognitive development, school performance, and future productivity. Despite the government's efforts in poverty and hunger reduction, the Philippines continuously sustains a high prevalence of undernutrition among school-age children. This study aims to determine the influences of different factors on the weight, height, and body mass index of school-age children in farming households. This study utilized data from the 2015 Updating of the Nutritional Status of Filipino Children and Other Population Groups of the Food and Nutrition Research Institute. This study includes 1689 school-age children from farming households who satisfied the inclusion and exclusion criteria. The findings of this study suggested that household wealth index, household size, and food security status affected the weight of school-age children in farming households. It was also observed that household wealth index, size, food security status, and dietary diversity status significantly affect the height of school-age children in farming households. Lastly, the wealth index, the age of children, and the number of 0-10 years old children in farming households significantly affect their body mass index. The findings of this study provide empirical evidence that the most important underlying causes of undernutrition among school-age children belonging to farming households could guide policymakers and program planners to craft interventions that target this vulnerable group.