Background:Previous studies have been inconclusive concerning the effect of active transport on BMI. Our objective was to investigate the association between travel mode and BMI in a large community-based sample of Danish adolescents.Methods:A cross-sectional survey on health and lifestyle was distributed to all pupils from the 7th to 9th grade (12–16 years of age) in the municipality of Odense, Denmark.Results:Cycling to school was associated with 0.38 lower BMI compared to passive travelers (P = .006) after multivariable adjustment. Cycling to school was associated with 0.55 lower odds of being overweight (P < .001) and 0.30 lower (P < .001) odds of being obese compared to individuals using passive transport. Walking to school was associated with 0.65 lower odds of being overweight (P = .006). Post hoc pairwise comparisons of ethnicity revealed that adolescents of foreign ethnicity were more likely to be walkers or passive commuters (75.14% vs. 29.72%) than cyclists (24.86% vs. 70.28%; P < .001) compared to subjects of Danish ethnicity.Conclusions:Cycling to school was associated with lower BMI and lower odds of being overweight or obese compared to passive travel in Danish adolescents, whereas walking to school was associated with lower odds of being overweight.