In this study, the construct of motivation to lead (MtL) is considered as a predictor of leadership training effectiveness. MtL, the individual preference to take on leadership roles, is a motivation that specifically relates to the content of leadership training. A total of 132 managers participated in a longitudinal follow-up study. The influence of MtL on training effectiveness is explained by a serial mediation process. Individuals high on MtL benefit more from training by acquiring more leadership competencies, which in turn results in more effective leadership behavior and ultimately higher training effectiveness 1 year later. Understanding the process through which trainees' individual MtL influences building up competencies is important for identifying mechanisms that drive training effectiveness. Organizational support is revealed to further enhance this training process by moderating the influence of MtL on leadership competencies. From a practical perspective, MtL is important for leadership training effectiveness and measures should be taken to enhance MtL.