This UNDP guidebook presents an approach to help a broad range of development practitioners prepare for, engage in, and manage systems transformation using a portfolio approach in complex development spaces. We developed this guidebook as a way to formalize our process and learnings to date, and leverage these to support others as they initially contemplate—and eventually work towards implementation of a portfolio-based approach for addressing complex development challenges in their own context. It captures the on-the-ground applied learning from a United Nations Development Programme (UNDP) sponsored project throughout Asia-Pacific from October 2019 to September 2021.