This cross-sectional study aims to examine the relationship between perfectionism and mental well-being and the mediating role of self-confidence. A total of 277 athlete-students, 166 males and 111 females, aged between 18 and 30, who were studying at different educational levels in the 2022-2023 academic year, participated in the study. Participants completed the perfectionism, confidence, which is a sub-dimension of the mental resilience scale, and mental well-being scales through an online questionnaire. Data were analyzed using descriptive statistics, Pearson correlations and mediation analysis. The results showed that there was a negative relationship between perfectionism and mental well-being. Likewise, a positive relationship was found between self-confidence and mental well-being. The findings also revealed a negative relationship between perfectionism and self-confidence. Mediation analysis showed that self-confidence played a partial mediating role in the relationship between perfectionism and mental well-being. This study has important implications for interventions aimed at improving mental well-being in student athletes. Focusing on improving self-confidence and providing support to individuals with perfectionistic tendencies has the potential to increase mental well-being. Furthermore, programs that aim to increase athletes' self-confidence, interpersonal relationships, self-awareness, and skill development may also support mental well-being. In conclusion, this study shows that self-confidence mediates the relationship between perfectionism, self-confidence and mental well-being. Understanding and addressing these relationships provides important information for developing interventions and programs that promote mental well-being in university students.