This summary report presents the final findings from the independent evaluation of the Foreign, Commonwealth & Development Office’s (FCDO) Development Impact Bonds (DIBs) Pilot Programme, which supported three DIBs in humanitarian rehabilitation, poverty graduation and education. Drawing on evidence from programme documentation, interviews, comparative analysis and three waves of evaluation conducted between 2019 and 2022, the report assesses how the DIB model influenced programme design, delivery, performance, effectiveness and organisational learning. It examines the distinctive effects of outcomes-based financing, including risk sharing, adaptive management, performance monitoring, collaboration and innovation, while analysing transaction costs, value for money and scalability. The report concludes with lessons on when DIBs are most appropriate, recommendations to improve their design and governance, and options for simplifying and expanding outcomes-based financing in international development.