PurposePrior research and theory have shown that transformational leadership can be developed through leader development programs (LDPs). To explain how this happens, research suggests a strong connection between an individual’s leader self-concept and their leadership behavior that can be manipulated through LDPs. The purpose of this article is to delve deeper into this phenomenon to understand how development occurs and to better understand how an LDP can improve leadership behaviors by influencing one’s self-concept and ultimately reduce the training transfer gap. As a broader goal, this article contributes to the existing literature on the value proposition of investing in LDPs.Design/methodology/approachWe conducted an explanatory sequential design mixed-methods study to measure the development of participants and the impact of the program. The quantitative phase of the study used self-report surveys to measure the LDP’s impact on participants’ transformational leader behavior (TLB) and concept of themselves regarding leadership, their leader self-views (LSVs). The study also measured the relationship between LSVs and later enactment of leadership behaviors as the second hypothesis. The subsequent qualitative study was designed to understand the mechanisms that might explain the quantitative results.FindingsThe study’s empirical findings indicate a positive relationship between LSVs (efficacy, self-awareness and identity) and distal leader development outcomes (TBLs). The study’s findings also provide support for the claim that LDPs convert knowledge and skills into TLB, expanding an individual’s capacity to be effective in leadership roles and processes (Day & Dragoni, 2015). Qualitative results also show LDPs improve leader behavior by influencing their self-efficacy via providing tools and knowledge as well as building experimental mindset.Originality/valueBy showing LDPs' long term impacts, this paper demonstrates why short-term leadership development programs are worth investing.