Background: While the school leader's role is undoubtedly instrumental in school effectiveness, the specific influence of formal leadership on pupil learning is indirect and can be difficult to determine. Research findings suggest that school leaders can influence school organisation and pupil learning by acting catalytically, thus unlocking their schools' existing potential. In school-based development, school leaders and their staff undergo a workplace development process, using school resources to contribute to it. Purpose: This article explores the concept of leadership in school-based development, focusing on leading teacher learning processes in relation to pupil learning. The research problem is formulated in the following question: How is the school leader's role enacted and experienced when enhancing teachers' learning in school-based development? The intent of the study was to further the understanding of leadership in school-based development. Sources of information and method: A qualitative interview study was conducted with teachers and leaders from three lower secondary schools, roughly 2 years after the schools participated in a formal school-based development project which was initiated by the Norwegian education authority. To present the findings based on the collected data, narrative texts were constructed. Findings: The findings draw attention to the importance of leaders' participation in the teacher learning processes of school-based development. The study highlights the importance of leaders building trust in their schools: development processes must be collegium-rooted with common goals for the whole school. The interplay of culture, structure and content is found to be necessary for successful school-based development. Furthermore, school leaders need to balance internal and external accountability, moving school practices towards local goals, which are constructed within national overall aims. Conclusions: The study suggests that leaders require an overview of developmental processes to manage to support and progress development; leadership needs to be distributed. Further research on leaders' learning in relation to school-based development can generate knowledge that serves as a thinking tool, thereby informing leaders' actions in support of school-based development.