Tobacco 21 laws may reduce smoking and tobacco-related health disparities among youth in the U.S

•Using a nationally representative dataset we found Tobacco 21 (T21) laws were associated with a lower likelihood of smoking participation among 12th graders.•The association between T21 laws and the reduction in the likelihood of youth smoking was especially strong among Hispanic/Latino/a/e individuals and youth with parents that had lower levels education and 12th graders that did not plan on attending college.•T21 laws show promise in potentially reducing tobacco-related health disparities in the United States. The goal of our study is to understand the impact of Tobacco 21 (T21) laws on youth smoking and health equity. We conducted modified Poisson regression models using 2014–2019 Monitoring the Future data to measure the impact of attending school in a county 100% covered by a T21 law versus counties with