Aims: To analyze the available evidence on the prevalence of physical inactivity among Brazilian adolescents by means of a systematic review of observational studies. Method: They were used 3 databases and 3 virtual libraries with key descriptors of this subject. After applying the eligibility criteria 22 item were identified. Results: the studies showed that over 50% of adolescents are inactive, identifying a higher prevalence in female adolescents. Furthermore, several factors may interfere in this practice (age, sex, socioeconomic status and sedentary behavior). Conclusion: The physical activity acts as a protective agent for health, becoming important at the adolescence, thus promote public and private policies will serve to enhance the physical activity in this population encouraging healthy habits into adulthood.