Introduction. Viewing television advertisements for unhealthy foods and beverages increases childhood obesity risk. Black and Hispanic youth are exposed to more television than white youth. Eliminating the current U.S. tax subsidy for marketing unhealthy foods and beverages to children was previously found to be a cost saving intervention for reducing childhood obesity, but its impact on racial/ethnic disparities is unknown. Methods. The Childhood Obesity Intervention Cost Effectiveness Study (CHOICES) microsimulation model estimated the cost-effectiveness of eliminating the marketing tax subsidy for preventing childhood obesity. Using 1,000 model iterations, we projected reductions in childhood obesity prevalence and healthcare costs in the year 2025 attributable to the intervention in the 2015 U.S. population, stratified by race/ethnicity.. Results. Closing the marketing tax loophole was estimated to result in about twice the reduction in the prevalence of obesity among non-Hispanic Black (0.28 percentage point reduction, 95% UI: 0.11, 0.44) and Hispanic youth (0.23 percentage point reduction, 95% UI: 0.09, 0.36) compared to non-Hispanic white youth (0.13 percentage point reduction, 95% UI: 0.05, 0.21). Childhood obesity prevalence reductions for non-Hispanic Black and Hispanic youth were higher in 100% of model iterations, suggesting high potential for significant impact on reducing disparities. Similarly, healthcare cost savings per dollar spent from the intervention were projected to be twice to three times larger for Black ($59.10) and Hispanic youth ($60.90) compared to white youth ($21.87). Discussion. Eliminating the tax subsidy for advertising unhealthy foods and beverages to children could reduce racial/ethnic disparities in childhood obesity and save society money.