This systematic review analyzed the prevalence of physical inactivity, sedentary behaviors and unhealthy eating habits among Brazilian adolescents. Searches were conducted in five databases (Lilacs, SciELO, Medline, Web of Science, and Google Scholar) and in the references cited in the articles retrieved. The literature search yielded 5,872 potentially relevant titles and a total of 69 studies met all the inclusion criteria. The risk behavior most often evaluated was physical inactivity (48/69; 69.6%), and its prevalence rate ranged from 2.3% to 93.5%. Twenty-eight studies estimated the prevalence of physical inactivity at over 50%. Most studies observed the prevalence of greater physical inactivity among girls. The prevalence of sedentary behaviors (lengthy screen time or TV use) was also frequently over 50%. Several variables were used to identify unhealthy eating habits, and some criteria/studies have indicated unhealthy eating habit estimates at close to 100% among adolescents. In conclusion, the estimates of these risk behaviors among Brazilians adolescents were very close to or even greater than those found in developed countries in several studies analyzed in this review.