Introduction: An increase in excess body fat and a decrease in the number of hours of sleep per day are health problems affecting the paediatric population. Objective: To estimate the combined prevalence of overweight and insufficient sleep/day in adolescents, and the association with sociodemographic characteristics, physical activity and sedentary behaviour. Methods: A cross-sectional school-based study was conducted with 1,132 participants from 14 to 19 years old in São José, Santa Catarina, Brazil. Body fat was assessed by body mass index (BMI) and classified by the Z-score, while adolescents reported the total hours of sleep/day. Sociodemographic data, physical activity and sedentary behaviour were collected by self-filled questionnaire. Results: The simultaneous prevalence of overweight and insufficient sleep/day was 17.5%. The factors associated with this condition were to meet the recommendations of the practice of physical activity per week, participate in gym class twice/week and period greater/equal to four hours/day in front of the screen. Conclusion: Guidelines in the school environment in relation to health problems posed by weight excess and the amount of insufficient hours sleep can be present when recommendations on physical activity and sedentary behaviour are given to students
