In the international climate policy arena, Ecosystem-based Adaptation (EbA) has become the preferred adaptation approach to climate change in the least developed and developing countries. Its perceived strength lies in the premise that adaptation strategies need to address both ecosystems and livelihoods simultaneously, given these are crucially intertwined and both under a threat from climate change. While EbA has certainly made progress as an adaptation approach, a lack of understanding still exists how EbA approaches contribute to ‘effective’ adaptation, including the circumstances where they face constraints and limits. Furthermore, implementation of EbA approaches ideally requires a level of understanding about ecosystem structure, productivity and dynamics, and how these are affected by climate change and other direct anthropogenic stressors, that are rarely available in developing countries. This paper aimed to synthesise the current knowledge in the emerging body of EbA specific literature on the kinds of constraints that hamper the use of EbA. Our analysis examined the following constraints: economic and financial, governance and institutional, social and cultural, knowledge constraints and gaps, and physical and biological constraints and limits. The identified constraints demonstrate the complexities in developing, implementing, monitoring and evaluating EbA and propose significant further areas of research, including the need to provide well-documented case studies of EbA, which crystallise the main lessons learned such as practical challenges in designing and implementing EbA projects and research programs.