Objective: Adolescent athletes are more prone to mental health issues because of the requirements of sports participation such as sports injuries and coach expectations. Therefore, the present study investigated the relationship between mental strength and competitive state anxiety in adolescent athletes with the mediating role of emotional self-efficacy and mindfulness. Methods: This study was descriptive through structural equations; the relationships between latent variables alongside observed variables were addressed, and validation was performed using fit indices (CFI, AGFI, PNFI, GFI, and RMSE). Its statistical population was all the professional and semi-professional athletes in Mashhad who had a history of participating in sports activities in 2023. The participants consisted of 321 athletes who were selected through purposive sampling. Competitive state anxiety questionnaires of Martens et al., the mental toughness of Sheard et al., Ryan and Brown’s mindfulness, and the emotional self-efficacy of Beverly et al. were used to collect data. Results: As the results showed that the mental strength (β = −0.25; T = −3.65), emotional self-efficacy (β = −0.35; T = −5.38) and mindfulness (β = −0.18; T = −2.85) have a direct effect on competitive state anxiety in adolescent athletes. Mental toughness through emotional self-efficacy (T-Sobel = 6.390, P < 0.01) and mindfulness (T-Sobel = 7.931, P < 0.01) has an indirect effect on competitive state anxiety in adolescent athletes (P < 0.01). Conclusions: Mental toughness, emotional self-efficacy, and mindfulness play an important role in the level of competitive state anxiety of adolescent athletes. Therefore, it is useful for identifying adolescent athletes who are at higher risk of developing mental health problems such as competitive state anxiety. The officials of sports clubs, organizations, and programs of athletes can examine the variables of mental toughness, emotional self-efficacy, and mindfulness of athletes, and use them to identify athletes who may need more support.
