Leadership development has become increasingly important in both academia and the corporate world in recent years (Day et al, 2014). The leadership development literature, while expanding, is limited in its provision of a systemic approach to individual leadership development. Evidence from research conducted on leadership development via coaching, mentoring, on the job experience and 360 degree feedback suggest that leadership development can be supported by deploying these practices in a programme for leadership development (Ladegard and Gjerde, 2014; Yip and Wilson, 2010). Kegan and Lahey (2010) contend that the underlying ‘operating system’ used for effective leadership development has not been addressed in recent leadership development approaches. This has led to calls for research to connect the leadership development and adult development literatures (e.g. Dinh et al, 2014). This study explores the leadership development of 20 Senior Managers participating in a leadership development programme within a financial services setting during the financial crisis within Ireland. The purpose of the programme was to develop authentic leadership among participants and the study compares the participants’ development with the development of a Control Group of 10 Senior Managers who did not participate in the programme. Leadership development is measured through a constructive developmental lens using the Subject Object Interview (SOI) methodology (Kegan and Lahey, 1984) to assess development. This study shows that the application of Constructive Developmental Theory (CDT) to the field of leadership development research provides a meaningful lens through which the authentic development of individual leaders can be better understood. From a practice perspective, its findings suggest that leadership development interventions should be tailored to suit the developmental stage of participants at the outset of any intervention. These findings highlight that focusing on ‘development’ as the criterion of interest rather than leader performance can be beneficial to demonstrate the impact of leadership development programmes.