BACKGROUND: Exposure to environmental tobacco smoke increases pediatric asthma severity. Strict, state-level tobacco control reduces smoking. The Child Asthma Call-Back Survey (Child ACBS) is a nationally representative survey of the guardians of children with asthma. The American Lung Association’s annual State of Tobacco Control report grades tobacco control laws in each state including a tax grade (cigarette excise tax relative to the national mean), and a smoke-free air grade (number of locations where smoking is prohibited). METHODS: We joined Child ACBS data from 2006 to 2010 with corresponding state and year tobacco grades. In the primary analysis, we investigated the effect of state tax grades on a child’s asthma severity by using a logistic regression model adjusting for year. A secondary analysis assessed the impact of smoke-free air grades on in-home smoking. RESULTS: Our analysis included 12 860 Child ACBS interviews from 35 states over 5 years, representing over 24 million individuals. We merged 112 unique State of Tobacco Control grades with patient data by state and year. A higher tax grade was associated with reduced severity (adjusted odds ratio = 1.40; P = .007, 95% confidence interval: 1.10–1.80). A better smoke-free air grade was not associated with decreased in-home smoking after adjusting for confounding by income and type of residence. CONCLUSIONS: A stronger tobacco tax is associated with reduced asthma severity. Further study is needed to determine the effect of smoke-free air laws on in-home environmental. This work supports ongoing efforts to strengthen tobacco control through federal and state regulations.