Cost Benefit Analysis (CBA) is underutilised in assessing Ecosystem- based Disaster Risk Reduction (Eco-DRR) interventions, the protocols used are not always rigourous and the analytical framework is unclear. However, CBAs which follow best practices could be extremely beneficial and helpful to policy makers in establishing priorities for Eco-DRR interventions. A robust and systematic economic analytical approach might be useful, if not necessary, to justify large upfront investments and promote the implementation of this type of risk reduction intervention at an even broader scale. Identifying a common core of best practices for CBA applied to Eco-DRR would also increase comparability between studies, reproducibility of assessments, and facilitate much needed external review. The purpose of this chapter is to (i) outline the fundamental principles and best practices of rigourous cost-benefit analysis (CBA) applied to ecosystem-based adaptation (EbA) and (Eco-DRR) interventions; (ii) review existing studies; and – based on this review of past work – (iii) outline the possible areas of improvement to strengthen future CBAs of Eco-DRR projects.