This purpose of this paper is to surface findings from a review of pertinent major research in Singapore and highlight the system-wide impact of in-service leadership mentoring over a sustained period of time. Beyond the transmission of knowledge and experience, sustained leadership mentoring generates a pervasive network to create learning in the development of aspiring school principals. Findings also reveal that protégés appreciate the role-modeling of their mentor principal in relation to service in leadership and the facilitation of learning. The nurturing and consolidation of relationships in mentoring actively promote interactions among peers in educational administration and leadership. The impact of leadership mentoring on the education system in influencing school leaders is substantial, over and beyond the period of its structured implementation.