The practice of mentoring has become increasingly influential as a mechanism for creating communities of learning that develop leadership partnerships and capability within, and across global educational settings. This study examines the role of mentoring in building such partnerships and capabilities within two discrete contexts: one, amongst students and two, amongst school leaders. The paper provides a broad overview of the mentoring literature within an educational leadership context.  It then presents two case studies that highlight the ways in which mentoring builds both leadership capability and agency.  A Finnish case study exemplifies the impact of school leaders mentoring senior students to develop leadership capability and capacity.  A New Zealand case study highlights how mentoring school leaders has facilitated the building of agentic learning communities with increased social capital.  The research was guided by a qualitative case study design and used face-to-face interviews, document analysis and focus group discussions as the primary data collection tools.  The process of analysis sought to describe the dynamic pattern of relationships between mentors and mentees.  The findings are significant for educational leaders who are interested in integrating a theoretical and practical framework of mentoring, to enhance both their own, and their students’ leadership capability. There remains abundant scope and reason to continue inquiring into the possibilities of mentoring relationships as a strategy for growing leadership capacity and agency in education contexts.