Although the literature on leadership is abundant and funds spent on leadership training have consistently increased over time, only 13% of organizations report that they have done a quality job with increasing leadership skills. Senior executives asserted that only 11% of leadership development interventions achieved and sustained the desired results (Jian, Xu, Houghton, Kulich, 2021). Building global leadership has been rated as a highly urgent and important need across all levels, in all geographies. This qualitative single-case study was the first in which the experiences and insights of highly trained leadership development experts (LDEs) certified as masters of The Leadership Challenge (TLC) were explored. The authors of the best-selling book, "The Leadership Challenge," and developers of the TLC educational workshop began conducting research and teaching in university settings more than 35 years ago. Despite this, empirical research is nonexistent related to the thoughts and practices of experts certified in TLC who increase leadership skills across all levels globally. This study was designed to explore leadership development through three lenses of TLC certified masters (CMs): (a) the personal lens of how LDEs develop themselves, (b) the professional lens of how LDEs evaluate program effectiveness through their participants' growth, and (c) a mentor or consultant lens of LDE's recommendations to new professionals to develop exemplary leadership, learning, and habitual practices. The study implications provide insights into practical ways to target efforts at what works in leadership development. Best practices were gathered from seasoned leaders to suggest actions organizations may take to transfer employee learning to the workplace. Of the 78 CMs listed on the TLC website as of May 2022, 18 participated in this study The four levels of training evaluation in the Kirkpatrick model were used to direct the interview questions to discover whether, and to what extent, TLC CMs use this evaluative framework. An iterative cycle of inductive analysis of more than 450 pages of single-spaced transcripts from participant narratives was triangulated with contextual data, including expert insights and website information. Member checking and subsequent conversations guided the development of 12 major themes. From this research, several unexpected discoveries were made; one being the tension between the Kirkpatrick model and the Leadership Practices Inventory 360 assessment. While TLC CMs have adopted the Kirkpatrick model's four levels of training evaluation, they have added at least two factors to help them with each level. Through qualitative interviewing and questioning in each stage of the process, TLC CMs believe the Leadership Practices Inventory proves that participants have learned and changed behavior to obtain Kirkpatrick's Level 4, results. Another unexpected finding was that TLC CMs develop themselves by engaging in personal reflection. This was surprising as TLC CMs do not teach the practice of personal reflection as it is not included in TLC curriculum. Implications of this study inform professional development practices for LDEs to support teaching, coaching, and facilitating future exemplary leadership practices. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]