Background Neighborhood design features have been associated with health outcomes, including the prevalence of obesity. Purpose This study examined the association between walkability and adolescent weight in a national sample of public secondary school students and the communities in which they live. Methods Data were collected through student surveys and community observations between February and August 2010, and analyses were conducted in Spring 2012. The sample size was 154 communities and 11,041 students. A community walkability index and measures of the prevalence of adolescent overweight and obesity were constructed. Multivariable analyses from a cross-sectional survey of a nationally representative sample of 8th-, 10th- and 12th-grade public school students in the U.S. were run. Results The odds of students being overweight (AOR 0.98, 95% CI=0.95, 0.99) or obese (AOR=0.97, 95% CI=0.95, 0.99) decreased if they lived in communities with higher walkability index scores. Conclusions Results suggest that living in more-walkable communities is associated with reduced prevalence of adolescent overweight and obesity.