The link between sleep and Body Mass Index (BMI) is poorly understood and existing literature on the topic is contradictory. Aim: To investigate the association between Body Mass Index [BMI] and sleep habits in adolescents in Sweden. Methods: This cross-sectional study uses data obtained from the self-reported questionnaires of 1518 (50.7% female) 13- to 15 year-olds in southern Sweden. Questions were on sleep and lifestyle habits and general demographics including height and weight. Multiple logistic regression analysis was used to analyze sleep duration, bedtime and rising time, controlling for covariates. Results: The only sleep related variable associated with overweight/obesity was sleep duration on weekends, where longer sleep duration decreased the likelihood of being overweight or obese. Conclusion: This study found that longer sleep duration during weekends was associated with not being overweight. Modifying sleep habits in adolescents is a potential target for obesity intervention and this information is particularly well-suited for school nurses to disseminate to students and their parents.