Grounded in attachment theory and self-determination theory, this study aimed to examine whether basic needs satisfaction is a mechanism by which athletes' insecure attachment styles are associated with levels of well-being.Athletes (N = 430) from a range of sports and competition levels completed a multi-section questionnaire to assess the main variables of the study.Bootstrap mediation analysis revealed that athletes' perceptions of satisfaction of basic psychological needs generally mediated the association between their attachment styles and well-being. Moreover, the indirect effect of athletes' experience of the satisfaction of basic needs on well-being was greater within the parental relational context than within the coaching relational context.Overall, the findings from the study highlight that the integration of attachment and self-determination theories can promote understanding of relational process in sport.