Athletic identity (AI), the degree of personal connection to sport, is well-described in adult research; however, this social trait has been less studied in younger age groups. This systematic review describes epidemiological characteristics of AI in youth athletes. PubMed, Embase and PsycInfo were searched to identify AI studies involving quantitative athlete identity outcomes and cohorts 22 years and younger. The search strategy was developed for each database using the Boolean method. PRISMA guidelines and the Appraisal Tool for Cross-Sectional Studies (AXIS) were utilized. Ten out of ninety-one studies met inclusion criteria. AI scores differed by race/ethnicity. Two studies found increased AI during adolescence compared to later in ones’ training. Mental health-focused studies revealed higher AI levels protect against burnout, but in injured athletes, increased depression risk. Transitioning to a higher level of play during adolescence can correlate with stronger senses of AI. Further research should explore the concept of athletic identity saliency as one moves through an athletic career or training program and how thoughts of perceived success, professional progression, recruitment prospect or injury affect levels of athletic identity.