ObjectiveTo analyze sources of racial and gender disparities in adolescent obesity prevalence in the United States using Oaxaca–Blinder decomposition.MethodsData were obtained from the National Youth Physical Activity and Nutrition Study, a 2010 nationally representative study of 9th‐12th grade students. Obesity status was determined from objective height and weight data; weight‐related behaviors and school, home, and environmental data were collected via questionnaire. Oaxaca–Blinder decomposition was used to independently analyze racial and gender obesity prevalence differences (PD), i.e., comparing Black girls to White girls, and Black girls to Black boys.ResultsOverall, measured characteristics accounted for 46.8% of the racial PD but only 11.9% of the gender PD. Racial PD was associated with Black girls having less fruit/vegetable access at home, obtaining lunch at school more often, and playing fewer sports than White girls. Gender PD was associated with differential associations between physical activity (PA) measures—including total activities in the past year and days of moderate to vigorous physical activity (MVPA) in the past week—and obesity.ConclusionsSchool lunch and home food environmental variables accounted for racial disparities, but not gender disparities, in obesity prevalence. Gender differences in mechanisms between PA and obesity should be explored further.