This chapter highlights the roles of multiplier firms and megaprojects in leading change for sustainability in the built environment. Multiplier firms are organizations that offer on-going sustainability solutions to a range of client organizations. Megaprojects are finite-duration initiatives involving multiple organizations in the delivery of a large-scale development, such as a new ecologically sustainable city. Drawing on illustrative case studies of multiplier firms and megaprojects engaged in sustainability-related initiatives, the chapter also explores the value of learning logic—in contrast to blueprint logic—for leading change. Blueprint logic describes a top-down approach to change that relies on well-developed plans, while learning logic involves experimentation, iteration, and sourcing ideas widely to make progress on complex goals. A learning logic is appropriate for leading change for sustainability, because effective techniques for success are not yet know