Purpose: Leadership for the implementation of an educational innovation in Singapore was examined by integrating distributed leadership with an ecological perspective of leadership and analysed using the third generation of cultural-historical activity theory. Research Method: The study adopted the naturalistic inquiry approach of a case study of a cluster of six elementary schools in the process of diffusing an educational innovation over one academic year. The research team observed six open classroom sessions and two review sessions at the cluster level. A total of two Ministry officers, one Master Teacher, 10 school leaders, 12 key personnel and 21 teachers were interviewed. Findings: The use of cultural-historical activity theory as an analytical lens provided insights into how different activity systems at the ministry, cluster, and school levels interact in providing leadership for the implementation of the innovation, the tools utilised, the rules/norms which enabled or constrained the innovation's implementation, and the evolving nature of the leadership provided. The study affirms the value of incorporating an integrative perspective in the analysis of leadership and the value of cultural-historical activity theory in unpacking the distribution of leadership across interrelated activity systems, and in highlighting the temporal evolutionary nature of leadership.