Résumé : This study analyses the role of sport trade unions in labour relations taking basketball as a case study. It explains, in part, why unions organizing athletes have developed significantly in recent years while traditional unions overall are in decline. Historically, employer-employee relationships in sport were based on employment rules that stood outside the scope of labor law, in both American and European contexts. This reality has been altered over the last 20 years by an increase in the involvement of the justice sector within sport regulation. This change can be observed through the challenges to employment rules that athletes have brought before courts and successful attempts to modify (or even suppress outright) rules deemed too constraining. Interestingly, athletic associations have benefited from these individual actions and their judicial outcomes which have combined to increase their (collective) power and their ability to conclude collective agreements. Although these new collectivized settings have resulted in an improvement of working conditions across the spectrum of organized sports, the unions represent an instrument rather than a direct force by which judicial decisions regarding individual cases can be expanded to cover the entire unionized collective. Finally, this specificity could explain why these collective agreements were often associated with a significant increase in the wages of the most talented athletes and, hence, wage dispersion.