BACKGROUND: Sports injuries are linked to negative impacts on mental health and well-being, including depression, anxiety, stress and lower quality of life. Conversely, poor mental health and well-being have been found to increase the risk of sports injury, injury severity and time taken to recover. Although existing research indicates these associations in athletes broadly, the nature and directionality of these relationships among adolescents are not well characterised. A related limitation is that much of the existing evidence, in both children and adult athletes, is cross-sectional in design, limiting our understanding of causal directionality. Given the high rates of sports participation and the specific risk factors for injury in this demographic, as well as the growing concern about adolescents' mental health and well-being worldwide, this complex relationship warrants greater attention. OBJECTIVE: We aimed to examine the bidirectional relationship between sports injuries and mental health and well-being in adolescents aged 10-24 years, and potential mechanisms of this relationship. METHODS: This systematic review and meta-analysis was registered on PROSPERO (ID: CRD42023374807). Literature searches were performed according to PRISMA (Preferred Reporting Items for Systematic reviews and Meta-Analyses) guidelines by searching PsycINFO, Web of Science, ERIC, CINAHL, MEDLINE, Embase, Cochrane Library, SPORTDiscus, PEDro, Elicit and Google Scholar. Articles were included if they were quantitative, published in English between 1990 and 2023, focused on young athletes aged 10-24 years, measured mental health/well-being and were an all-complaints sports injury that ranged across all levels of sport. RESULTS: Of 397 studies screened, 84 studies were included. The final sample included 221,095 adolescents and young people. A narrative synthesis indicated that sports injuries were associated with worse mental health and well-being in the majority of studies, and vice versa. Meta-analyses revealed that sports injury incidence was significantly associated with worse mental health/well-being (Zr = 0.34, 95% confidence interval 0.17, 0.50), and concussion incidence was significantly associated with worse mental health/well-being (Zr = 0.19, 95% confidence interval 0.08, 0.30), with no evidence of publication bias. Conversely, worse mental health/well-being was associated with a significantly increased risk of sports injury incidence (odds ratio = 1.54, 95% confidence interval 1.13, 2.10). However, after accounting for potential publication bias, the pooled association between mental health/well-being and sports injury risk was no longer statistically significant, highlighting the need for caution in interpreting this relationship. Regarding mechanisms, a small number of studies revealed psychosocial factors (e.g. athletic identity, social support) that could influence this reciprocal relationship. CONCLUSIONS: We found evidence for a bidirectional relationship between sports injuries and mental health in adolescent athletes. Further research is needed to elucidate the mechanisms underlying this relationship. Early interventions focusing on supporting mental health after sports injury, and addressing pre-existing mental health issues to reduce the risk of subsequent injury, should be tailored towards psychosocial mechanisms that particularly impact adolescent athletes.