We propose that distinct leadership competencies differ in their development over time. Extending the integrative model of leader development (Day et al., 2009), we further propose that leader identity will form complex relationships with leadership competencies over time. To test these propositions, we use longitudinal data (i.e., 5 months, four measurement points) of the 80 in total high-potential executives in a corporate leadership development program. We find a significant difference in the initial levels and the changes of eight distinct leadership competencies. We also find that leader identity relates to the development of certain – but not all – leadership competencies. Finally, we demonstrate the importance of developing leadership competencies by linking them to career advancement (i.e., job promotion). These findings are discussed in light of their theoretical and practical implications.