After several decades of development assistance, policymakers and the civil society are questioning the effect of development assistance. What results are these huge amounts of development assistance actually having? In the early 2000s, an effort was made to improve the effectiveness of development cooperation projects through results-based management in order to respond to criticism surrounding the effectiveness of assistance and scientifically demonstrate the performance of development projects. The development agencies, such as WB, USA, and Japan, have begun to demonstrate the effectiveness of development cooperation projects by rigorously assessing the impact of individual development projects on beneficiaries. It is time for Korea to adopt rigorous evaluation, such as impact evaluation, to enhance development effectiveness through evidence-based policy making. The first step for that would be to build knowledge about the importance of rigid evaluation among stakeholders. Second, more systematic selection process is needed. This is not to say that Korea's ODA evaluation system should be immediately revised and an impact evaluation conducted on all aid projects. In the short term, it is considered to implement the impact evaluation of small and innovative project to strengthen the capacity of the evaluation. In the mid-to-long term, however, a strategic assessment and feedback process should be set up to evaluate the impact of a large project that is a flagship initiative with influential results.