Objective: To evaluate trends in physical activity and sedentary behavior simultaneity among Brazilian students from 2009 to 2015 and its association with independent variables. Methods: This study presents a panel of 3 cross-sectional studies carried out in 2009, 2012, and 2015 (Pesquisa Nacional de Saúde do Escolar—PeNSE). The population was comprised of ninth-grade public and private schools students from Brazilian capitals. Physical activity and sedentary behavior variables were combined to create the outcome of simultaneity of these risk factors. Results: A large proportion of students were simultaneously inactive and sedentary in the 3 surveys. However, it was possible to observe a downward trend (2009: 56.4%; 95% confidence interval, 55.7–57.1; 2012: 53.7%; 95% confidence interval, 53.0–54.4; 2015: 51.9%; 95% confidence interval, 51.2–52.7). In 2015, estimates of physical inactivity and sedentary behavior simultaneity were greater than 48% for 20 out of 27 of the Brazilian states. Significant declining trends were observed among mideast residents, females, nonwhite, and those attending private schools. Only around 5%–7% of the adolescents were both active and nonsedentary in the 3 surveys. Conclusion: Despite of a slight decreasing trend in the proportion of Brazilian students simultaneously inactive and sedentary throughout the period, the prevalence remained elevated across the surveys.