This chapter describes the use of transformational leadership assessment, combined with the action research method, as strategies for developing leadership competencies in a healthcare institution (GS-Health) undergoing restructuring and seeking ONA accreditation. In the face of post-pandemic challenges, such as financial difficulties and the need to optimize processes, a misalignment was identified between current leadership practices and organizational requirements. To address these gaps, the action research cycle was implemented, focusing on the analysis of transformational leadership competencies among current managers and the development of specific leadership development pathways. The assessment revealed the need for leadership that fosters innovation, engagement, and adaptation to institutional demands, highlighting the inadequacy of previous training initiatives adopted by the Leadership Development Program (LDP). The action research approach enabled an iterative process of assessment, intervention, and evaluation, allowing for continuous adjustments in management practices and leadership training. The results indicate that strengthening transformational leadership—characterized by idealized influence, inspirational motivation, intellectual stimulation, and individualized consideration—can positively impact the quality of healthcare services. This study, therefore, presents a pathway for guiding the development of transformational leadership in organizations through diagnostic tools. Specifically, for healthcare management, this study proposes a focus on achieving results in quality indicators and, consequently, the potential for a positive impact on ONA accreditation.