Background: Sport-related concussions are a major public health problem with only 50% of concussed teens reporting their symptoms. The purpose of this systematic review was to identify individual and institutional factors that contribute to concussion knowledge, attitude, and reporting behaviors among US high school athletes. Methods: The Preferred Reporting Items for Systematic Reviews and Meta-Analysis protocol was used to direct the process of this systematic review. A search for English, peer-reviewed, quantitative studies published between 2010 and 2020 was conducted in 5 scholarly databases. The Joanna Briggs Critical Appraisal Tools were used to assess study quality. Results: Twenty-two studies met criteria for inclusion in this systematic review. The study designs were mostly cross-sectional (N = 18). Synthesis revealed individual factors including gender, age, race/ethnicity, grade level, and concussion history were associated with differences in concussion knowledge, attitude, and/or reporting behaviors. Institutional factors identified included school location, concussion education, access to an athletic trainer, sport played, and team climate. Six studies found concussion education had a positive impact on knowledge and reporting behaviors. Conclusion: This systematic review identified certain populations which may be more vulnerable to underreporting concussion symptoms; therefore, a targeted approach to education and management may be more effective.