Blended finance and public private partnerships are landmark mechanisms for sustainable development financing. They are flagged by development finance institutions as promising means to bridge the post-2015 development investment gap. However, the effectiveness of their potential contribution to financing the post-2015 development agenda remains far from certain. Not only do their definitions differ from one institution to another, but also their performance in leveraging funding and channeling it to the most needful goals and countries has not been properly assessed, mostly due to the lack of empirical evidence. In this chapter, we aim to explain why these two financing vehicles fall short of delivering on promises. We provide insight on some possible means to overcome their current limitations.