Background: Little is known about how interpersonal friend relationships are associated with obesity in young people, particularly with regard to how race/ethnicity, type of friendship, and sex affect the association between friends' and adolescents' weight status. This study examined associations in weight status among adolescents and their friends, exploring magnitudes of associations across friendship type, sex, and race/ethnicity. Methods: As part of EAT-2010 (Eating and Activity in Teens), friend nominations and anthropometrics were obtained from adolescents (n = 2099: 54% female; 80% nonwhite; mean age: 14.2 ± 1.9 years). Generalized estimating equation logistic regression models were used to test associations between adolescents' overweight/obese status and friends' (i.e., friend group, female friends, male friends, female best friends, and male best friends) overweight/obese status. Interactions by adolescent race/ethnicity were examined. Results: The majority of significant associations were observed among white female adolescents' who had a 22-40% higher prevalence of overweight/obesity if their friends were overweight compared to white females whose friends were not overweight. In contrast, there were few significant differences for other adolescent female and male racial/ethnic groups for girls and boys. Results for friend groups and best friends were generally similar to one another. Conclusions: The association between friend and adolescent overweight/obese status depended on adolescents' sex, race/ethnicity, and friendship type. Given the similarities among friends, obesity interventions targeting youth, especially white females, should consider involving friends.