Background: Lack of physical activity (PA) and high levels of sedentary behavior (SB) have been associated with health problems. Although PA is considered to yield substantial health benefits, the level of PA among adolescents is not sufficient. Adolescence is characterised by a decline in PA level. Many studies investigated the effectiveness of interventions promoting PA among adolescents, but majority of the interventions are multifaceted involving diet, PA etc. The aim of this study is to evaluate and review physical activity interventions to improve physical activity level, fitness, and health outcomes among adolescents. Methods: A systematic review was conducted to identify PA intervention studies published in the scientific literature for the past two decades. Four databases were searched, reference lists were scanned, and the publication lists of the authors of the retrieved articles were checked. Results: The literature searched identified 9 relevant studies. All interventions were delivered through the school setting of which one included the use of the internet. Five of the interventions included the use of objective measures. Three of the intervention were based on theoretical models while six of them are multicomponent approach which involved the use of objective measures. None of the interventions included direct family involvement. The main findings of the review were: (1) School-based interventions generally lead to short term improvements in physical activity levels; (2) A sustained and realistic intervention can increase adolescent physical activity; (3) Multicomponent means of increasing physical activity among adolescent is better Conclusion: The overall literature supports the short-term effectiveness of school-based physical activity intervention. However, evidence to show its long-term effect or sustainability is still shrouded. Therefore, it is exigent for studies to implement a long-term intervention plan while carrying out their studies.Background: Lack of physical activity (PA) and high levels of sedentary behavior (SB) have been associated with health problems. Although PA is considered to yield substantial health benefits, the level of PA among adolescents is not sufficient. Adolescence is characterised by a decline in PA level. Many studies investigated the effectiveness of interventions promoting PA among adolescents, but majority of the interventions are multifaceted involving diet, PA etc. The aim of this study is to evaluate and review physical activity interventions to improve physical activity level, fitness, and health outcomes among adolescents. Methods: A systematic review was conducted to identify PA intervention studies published in the scientific literature for the past two decades. Four databases were searched, reference lists were scanned, and the publication lists of the authors of the retrieved articles were checked. Results: The literature searched identified 9 relevant studies. All interventions were delivered through the school setting of which one included the use of the internet. Five of the interventions included the use of objective measures. Three of the intervention were based on theoretical models while six of them are multicomponent approach which involved the use of objective measures. None of the interventions included direct family involvement. The main findings of the review were: (1) School-based interventions generally lead to short term improvements in physical activity levels; (2) A sustained and realistic intervention can increase adolescent physical activity; (3) Multicomponent means of increasing physical activity among adolescent is better Conclusion: The overall literature supports the short-term effectiveness of school-based physical activity intervention. However, evidence to show its long-term effect or sustainability is still shrouded. Therefore, it is exigent for studies to implement a long-term intervention plan while carrying out their studieS.