The Supplemental Nutrition Assistance Program (SNAP) is the nation’s largest federal food assistance program. The goal of the program is to help low-income families afford a healthy diet. However, several studies have found that participation in SNAP is associated with lower diet quality and an increased probability of being overweight among adults. Poor diet quality and being overweight contribute to the metabolic syndrome, which is a cluster of risk factors that increases the risk of heart disease, diabetes, and stroke. Poor diet and diet-related health in children is particularly harmful because of their vulnerable lifestage. This project uses two research designs that take advantage of policy variation to better identify the relationship between SNAP participation and child nutritional health: difference-in-differences and regression discontinuity. The difference-in-difference design uses the increase in SNAP benefit amounts from the American Recovery and Reinvestment Act to understand the link between an increase in SNAP benefits and child nutritional health. The regression discontinuity design uses the SNAP income-eligibility criteria to understand how the diet-related health of SNAP-eligible youth differ from those just over the eligibility threshold. Within these designs, I also examine how food security status and age modify the connection between SNAP and child nutritional health. Chapter Two examines the relationship between SNAP and diet quality. I find that an increase in SNAP benefits is associated with lower diet quality in youth across levels of food insecurity, and in two age groups: toddlers aged 2-3 years and children aged 6-11 years. However, youth who experience very low food security consume less sugar-sweetened beverages and more fiber when compared to those just over the SNAP income eligibility threshold. Chapter Three analyzes the link between SNAP and weight outcomes. I find that an increase in SNAP benefits is associated with healthier weight outcomes in youth who experience marginal food security, in children younger than 6 years, and in adolescents aged 12 to 18 years. Chapter Four studies the connection between SNAP and risk factors for the metabolic syndrome. I find that SNAP-eligible youth have significantly healthier outcomes, but this relationship varies by food security status and age. Developing a better understanding of the relationship between SNAP participation and diet-related health outcomes in children can lead to refined federal nutrition policy. This is a critical policy question that has far-reaching implications for the health and well-being of the low-income children and families that rely on SNAP to help meet basic needs.