Abstarct: The present study aimed to investigate the effect of the coach–athlete attachment on athlete performance, with subjective well-being serving as a mediating variable. In terms of purpose, the study was applied research, and in terms of methodology, it employed a descxriptive-correlational and cross-sectional design. The statistical population consisted of all athletes participating in team sports in Razavi Khorasan Province, Iran. Using a convenience sampling method and baxsed on Klein’s sample size criterion, 184 athletes were selected as the study sample. Data were collected using the Coach–Athlete Attachment Questionnaire developed by Davis and Sophia Jowett (2013), the Athlete Performance Questionnaire developed by Charbonneau et al. (2001), and the World Health Organization-Five Well-Being Index (WHO-5) developed by Staehr Johansen (1998). The face and content validity of the instruments were confirmed by a panel of experts, while their reliability was established using Cronbach’s alpha and composite reliability coefficients. Data analysis was performed using SPSS and SmartPLS 3 baxsed on Partial Least Squares Structural Equation Modeling (PLS-SEM). The findings indicated that coach–athlete attachment had a significant positive direct effect on athlete performance. Moreover, coach–athlete attachment exerted a significant positive effect on athletes’ subjective well-being, contributing to improved psychological health, life satisfaction, and overall well-being. The results further revealed that subjective well-being had a significant positive direct effect on athlete performance. In addition, the mediating role of subjective well-being in the relationship between coach–athlete attachment and athlete performance was supported, indicating that part of the positive effect of coach–athlete attachment on performance is transmitted through enhanced subjective well-being. Overall, the findings highlight the importance of fostering positive, supportive, and trust-baxsed relationships between coaches and athletes. Strengthening the quality of the coach–athlete relationship not only enhances athletes’ subjective well-being but also contributes to improved athletic performance. Therefore, simultaneous attention to psychological factors and the quality of coach–athlete interactions can serve as an effective strategy for enhancing athletic performance and achieving sustainable sporting success.