The study analyzes retail food outlets and their association with overweight/obesity in schoolchildren from Florianópolis, Santa Catarina State, Brazil. The study used a cross-sectional design with a random sample of 2,506 schoolchildren from public (n = 19) and private schools (n = 11). Overweight and obesity were classified according to World Health Organization guidelines for 2007, and crude and adjusted analyses were performed using Poisson regression. Prevalence of overweight/obesity was 34.2%. In public schools, 19.6% of the children were overweight and 13.5% were obese, as compared to 22.4% and 11.1% in private schools. An association was found in the public school system between overweight/obesity and the use of bakeries for food purchases (p = 0.004). In the private school system, children of families that bought groceries at the supermarket showed 26% less overweight/obesity compared to those who did not (p = 0.003). The data show an association between some types of food outlets (supermarkets and bakeries) and prevalence of overweight/obesity in the school-age population.