For nearly a century, International Non-Governmental Organizations (INGOs) have spearheaded humanitarian relief and development efforts worldwide. However, the increasing complexity and interconnectivity of global challenges demand a fundamental shift in the operations of INGOs. Collaboration has emerged a key strategy in driving systemic change and addressing the root causes of complex issues. Leaders play a pivotal role in fostering these essential relationships and cultivating a collaborative ecosystem. While leadership remains paramount, there is a critical need to understand how INGO leaders can cultivate transformative collaboration, a collaborative approach aimed at addressing the root causes of complex issues and driving systemic change. This dissertation addresses this gap by exploring how INGO leaders foster collaboration for transformative change. Using a phenomenological research approach, the study conducted in-depth, semi-structured interviews with 16 high-level INGO leaders to investigate their lived experiences and insights regarding collaboration. The findings highlight the importance of a leader's collaborative posture, practice, and process in creating a culture of collaboration within and outside their organizations. Best practices that INGO leaders use include building trust and relationships, cultivating shared interest and ownership, and facilitating effective communication. The study also examines how INGO leaders measure success in collaboration, emphasizing both outcome-based and process-based indicators. The findings offer a valuable framework for understanding collaborative leadership in INGOs and provide actionable guidance for leaders seeking to enhance their collaborative practices, ultimately driving greater impact in addressing global challenges. Recommended Citation Manley, Colton, "Leadership best practices in fostering collaboration for transformative change in international nongovernmental organizations: a phenomenological study" (2024). Theses and Dissertations. 1468. https://digitalcommons.pepperdine.edu/etd/1468