Using data from the China Health and Nutrition Survey (CHNS), this study analyzes peer effects on obesity in a sample of 3- to 18-year-old children and adolescents in China. Even after a rich set of covariates and unobserved individual heterogeneity are controlled for, it is evident that such peer effects do indeed exist. These effects are stronger in rural areas, among individuals at the upper end of the BMI distribution, and especially among females. All else being equal, female adolescents whose peers have a higher BMI are less likely to consider themselves overweight, suggesting that peer effects may be working through changed societal bodyweight norms.