School improvement reforms aimed at achieving improved student learning remain high on the agenda for leaders across the globe. The purpose of this paper is to understand the leadership attributes that enable school leaders to bring about positive change. This qualitative study is based on interviews with school leaders (school principals and their deputy principals) and focus groups of six teachers in two case study schools. A realist approach is used to understand how leadership attributes spark related social mechanisms that lead to improved outcomes. Data analysis generated four leadership attributes: (1) valuing diversity, (2) support for staff, (3) collaborative leadership style, and (4) valuing teachers' professional learning. Each of these was found to have influenced decision-making and sentiment, which generated positive school improvement outcomes in the two case study schools. These findings have the potential to contribute to professional learning which can improve understanding of how leadership attributes in context bring about school improvement.