The effect of years of residence in the US on the weight of adolescents is unclear. We examined the association between generation (i.e. 1st, 1.5, 2nd, and 3rd) and weight indicators among Boston adolescents. Data are from a sample of 1,420 9-12th grade public school students in Boston, Massachusetts. We used self-reported information to calculate generation and weight characteristics (i.e., body mass index (BMI), BMI z-score, overweight status), and ran multivariate analyses to estimate the association between generation and weight characteristics, adjusting for race/ethnicity, gender, age and school. In pooled multivariate models, 1.5 generation, second generation, and third generation youth had significantly higher mean BMI scores and mean BMI z-scores than first generation youth. Second (RR 1.87, 95% CI 1.13-3.12) and third generation youth (RR 2.06, 95% CI 1.21-3.50) were also significantly more likely to be overweight than first generation youth. In multivariate models stratified by sex, this pattern persisted for females only. There is a positive, linear trend in BMI by generation that differs by gender. Mechanisms underlying this association should be addressed.