The correlates of coach-athlete relationship quality have been the focus of research for over a decade; however, little is known about the mediating and moderating mechanisms underlying these associations. The present study conducted a moderated mediation analysis to examine (a) the mediating role of communication strategies (via COMPASS) on the association between the quality of the coach-athlete relationship and athlete psychological needs satisfaction and (b) whether individual differences in athletes’ attachment style (secure, anxious, avoidant) moderates the mediational relationship. 350 Swedish athletes representing a range of sports and competition levels completed a multi-section questionnaire. Mediation and moderation analysis partially found that coach-athlete relationship quality and athletes basic psychological needs were associated via the COMPASS strategies of support, motivation, assurance and openness. It was also found that athletes secure attachment with their coach significantly moderated the mediated effects of motivation and support. These findings highlight the practical utility of motivation, support, openness and assurance strategies in enhancing the quality of the coach-athlete relationship. Moreover, these findings demonstrate that the attachment orientation of athletes towards their coaches play a significant role in determining what communication strategies to use to enhance both the relationship quality and an athlete’s competence, autonomy and relatedness.