One of the common aspects of professional culture is that teachers share their knowledge and experience only occasionally. However, principals can significantly contribute to reducing this weakness by demonstrating knowledge-sharing in their leadership role. It is critical for Iranian principals to play this role because there is some weakness among teachers due to certain context-specific conditions. The existing knowledge about this vital role is very scarce and cannot provide a complete and clear picture. The purpose of this study is to investigate this less-considered role in the context of Iranian primary schools. To this end, a basic qualitative approach was adopted. Using constant comparative analysis of the data obtained from interviews with successful principals, seven categories of themes emerged for knowledge-sharing leadership. This study not only supports the assertion that the principal's role in knowledge-sharing is indisputable but also contributes to the school leadership literature. Along with its implications for training programmes for principals, this study has several suggestions for theory and research.