Academic success in adolescence is a strong predictor of well-being and health in adulthood. A healthy lifestyle and moderate/high levels of physical activity can influence academic performance. Therefore, we aimed to assess the relationship between the physical activity levels and body image and academic performance in public school adolescents. The sample consisted of 531 secondary school students in Porto (296 girls and 235 boys) aged between 15 and 20 years. The study variables and instruments were satisfaction with body image (The Body Image Rating Scale), assessment of physical activity (International Physical Activity Questionnaire for Adolescents (IPAQ-A), assessment of academic performance (academic achievement), school motivation (Academic Scale Motivation). The statistical analysis performed was descriptive analysis, an analysis of covariance, and a logistic regression. Regarding the results obtained, although there was no association between physical activity level and academic performance, it was observed in 10th grade students that the school average was higher for those practicing group or individual sports compared to students practicing artistic expression. Regarding the level of satisfaction with body image, we found different results in both genders. Our results support the importance of an active lifestyle, with the presence of regular physical activity being an important factor in improving academic performance.