Epidemiologic studies have observed influences of the food environment near schools on children's overweight status but have not systematically assessed the associations by race, sex, and grade. The authors examined whether the associations between franchised fast food restaurant or convenience store density near schools and overweight varied by these factors using data for 926,018 children (31.3% white, 55.1% Hispanic, 5.7% black, and 8% Asian) in fifth, seventh, or ninth grade, nested in 6,362 schools. Cross-sectional data were from the 2007 California physical fitness test (also known as "Fitnessgram"), InfoUSA, the California Department of Education, and the 2000 US Census. In adjusted models, the overweight prevalence ratio comparing children in schools with 1 or more versus 0 fast food restaurants was 1.02 (95% confidence interval (CI): 1.01, 1.03), with a higher prevalence ratio among girls compared with boys. The association varied by student's race/ethnicity (P = 0.003): Among Hispanics, the prevalence ratio = 1.02 (95% CI: 1.01, 1.03); among blacks, the prevalence ratio = 1.03 (95% CI: 1.00, 1.06), but among Asians the prevalence ratio = 0.94 (95% CI: 0.91, 0.97). For each additional convenience store, the prevalence ratio was 1.01 (95% CI: 1.00, 1.01), with a higher prevalence ratio among fifth grade children. Nuanced understanding of the impact of food environments near schools by race/ethnicity, sex, and grade may help to elucidate the etiology of childhood overweight and related race/ethnic disparities.