The purpose of this study was to examine the relationships between transformational leadership style, affective commitment, and organizational citizenship behavior in the athletic director-coach relationship. This study particularly focused on the mediating effect of affective commitment on the relationship between transformational leadership and organizational citizenship behavior. Athletic head coaches in NCAA Division II programs (n ¼ 244) completed the questionnaires measuring perceptions of the transformational leadership style of their athletic directors, their affective commitment, and organizational citizenship behavior. The results revealed that perceived transformational leadership was positively associated with affective commitment, which, in turn, was positively associated with organizational citizenship behaviors. Further, the result of this study supported full mediation among the proposed variables in that affective commitment served as the underlying psychological mechanism in the relationship between transformational leadership and organizational citizenship behaviors. Implications for athletic departments in fostering head coaches' affective commitment and organizational citizenship behavior were discussed.