In recent years, researchers, policymakers, and practitioners have coalesced around educator evaluation as a critical lever for reforming teaching and learning. National and local policy changes have proliferated, and districts across the country are in the midst of reforming their systems for evaluating teachers. Old systems of evaluating educators, relying upon infrequent and unstandardized observations, are being replaced with more rigorous systems that include frequent observations with validated protocols, evidence of teacher practice and student outcomes, and measures of student learning. Given the fast-paced changes to educator evaluation policy and practice nationwide and what research suggests about organizational change in education, this paper explores the challenges to implementation that districts face and the strategies that early implementers have developed to address these challenges. The authors sampled 16 districts in 11 states across the United States that have embarked on significant efforts to implement more complex educator evaluation systems in line with the changing policy environment. Interviews with district leaders indicated that they face two overarching challenges: (1) changing district- and school-level culture and (2) building the district- and school-level capacity to implement a new, more rigorous evaluation system. In response to these challenges, the authors identified nine strategies that many districts have employed to manage the change process and build capacity. Interviews from the 16 districts suggest that there are many common challenges and much is to be learned from their efforts.